Ebook Toronto notes 2018 (34/E): Part 2

Part 2 book “Toronto notes 2018” has contents: Medical genetics, medical imaging, population health and epidemiology, plastic surgery, vascular surgery, rheumatology, respirology, psychiatry, otolaryngology, orthopedics, ophthalmology, neurosurgery, neurology,… and other contents.

Medical Genetics

MG

Spencer van Mil, chapter editor Sheliza Halani and Taraneh Tofighi, associate editors Arnav Agarwal and Sukhmani Sodhi, EBM editors

Dr Hanna Faghfoury and Dr Joyce So, staff editors

Approach to the Dysmorphic Child

Syndromes and Diseases 5

Large Genomic Changes

Single Gene Disorders

• Penetrance: extent that a gene is observably expressed in an individual that carries it

• Expressivity: extent of gene expression

• Genetic heterogeneity: genetic disorder can arise from different allele/locus mutations

• Phenotypic heterogeneity: mutations in the same gene resulting in multiple diverse clinical

manifestations and degree of severity

• Imprinting: epigenetic process that involves methylation or acetylation of DNA, affecting gene

expression

• Uniparental disomy: two full or partial copies of a chromosome from one parent and no chromosome

from the other parent

Mendelian Inheritance

• disorders caused by mutation of one or both copies (alleles) of a gene, inherited in one of two patterns

■ autosomal: when disorder is caused by genes on one of 22 pairs of autosomes (chromosomes 1-22)

■ X-linked: when disease is caused by a gene on the X chromosome

Triplet Repeat Expansions

• disorder in which trinucleotide repeats in certain genes exceed the normal number and result in altered

gene expression or production of an abnormal protein (e.g Fragile X syndrome, Huntington's disease)

Imprinting Disorders

• imprinted genes are expressed entirely from either the maternal or paternal allele, depending on the

gene (parent-of-origin gene expression)

• occur when a mutation disrupts the normally expressed allele of imprinted gene (e.g Prader-Willi

syndrome, Angelman syndrome, Beckwith-Wiedemann syndrome) or through uniparental disomy of

the normally silenced allele

Mitochondrial Disorders

• disorders caused by mutations of the DNA present in mitochondria or nuclear genes whose protein

products are important for mitochondrial function

• inheritance pattern of mitochondrial DNA mutations: mother passes on the defect to all her children;

father cannot pass on defect since embryo only receives mitochondria from the mother (in the egg)

Copy Number Variation

• difference in the amount of genetic material

■ decrease: deletion of a chromosomal region, leaving only one copy of the genetic material in that

region (e g 22q11.2 deletion syndrome due to deletion on chromosome 22)

■ increase duplication of a chromosomal region, resulting in more than two copies of the genetic

material in that region (e.g Potocki-Lupski syndrome due to duplication of chromosome 17p11.2)

• CNVs can be part of normal range of genetic variation

Acronyms

CF cystic fibrosis

CNV copy number variation

FISH fluorescence in situ hybridization

FTS first trimester screening

IPS integrated prenatal screening

ONTD open neural tube defect PKU phenylketonuria SCID severe combined immunodeficiency

Introduction to Genetics

Pedigrees

• diagrams that show the pattern/distribution of phenotypes for a genetic disorder within a family, often

across multiple generations

Figure 1 Common pedigree symbols

Genetic Testing and Counselling

• microarray analysis

■ array comparative genomic hybridization (CGH): a collection of DNA probes attached to a solid

surface to which test DNA hybridizes in order to determine copy number of DNA regions

■ microarray analysis can identify small deletions or duplications of genetic material anywhere in the

genome

■ commonly indicated when there is developmental delay OR two or more congenital anomalies

• FISH (fluorescence in situ hybridization): a DNA probe used to identify a gain or loss of chromosomal

material

• karyotype: microscopic analysis of chromosomes with a special stain that shows large changes in the

number or structure of chromosomes; can detect large CNVs

• Sanger sequencing: the ‘gold-standard’ method for identification of single nucletotide variants in short

DNA sequences (e.g the exons of the gene(s) known to cause suspected syndrome)

• next-generation sequencing: high throughput method to sequence exomes or whole-genomes; useful

when genetic syndrome is suspected, but diagnosis is unclear: increasingly used for multi-gene test

panels

• prenatal screening

■ offer optional prenatal screening before diagnostic testing

■ first trimester screening (FTS)

◆ biochemistry (b-hCG, PAPP-A)

◆ US est mate of gestational age and measurement of nuchal translucency

◆ screen for trisomy 21 and 18

◆ done between 11 and 14 wk, sensitivity=80-85%

■ integrated prenatal screening (IPS)

◆ ONTD, trisomy 21 and 18

◆ use results from FTS and combine with additional biomarkers completed between 15-21 weeks

(inhibin A, unconjugated estradiol, AFP, 2nd trimester b-hCG)

◆ improved sensitivity, reduced false positive rate compared to FTS

■ fetal anatomy scan

◆ US at 18-20 wk

• newborn screening

■ detect potentially fatal, treatable disorders before symptoms begin to allow for early therapy

■ performed on all newborns in Canada

■ heel puncture to collect blood

■ screens for CF, congenital hypothyroidism, congenital adrenal hyperplasia, SCID,

hemoglobinopathies, metabolic diseases, etc

this time but could

manifest disease later

Married/Partners Divorced/Separated Consanguinity Infertility

No Offspring

by choice Pregnancy

P P

Stillbirth (write SB and gestational age

if known)

SB SB

Spontaneous Abortion Termination of Pregnancy Ectopic Pregnancy ECT

Adopted Sibling Siblings (listed from left to right (oldest to youngest) Dizygous Twins (fraternal) Monozyous Twins (identical)

Whole-Genome Sequencing Expands Diagnostic Utility and Improves Clinical Management in Paediatric Medicine

Genomic Med 2016;1:15012

While the standard of care for neurodevelopmental and congenital malformations is chromosome microarray analysis for copy number variations, whole exome sequencing a lows the identification

of sequence-level mutations across all known coding genes Whole genome sequencing has been previo sly associated with a diagnostic yield

of ~25% for neurological disorders or congenital anomalies A recent study published in Genomic Medicine has demonstrated that whole genome sequencing exceeds other technologies in detecting genetic variants with a 34% diagnostic yield, a four-fold increase in molecular diagnosis relative to chromosome microarray analysis and a two-fold increase relative to all genetic testing protocols These results suggest that whole genome sequencing may be used as a first-tier molecular test in individuals with development delays and congenital abnormalities, with a higher diagnostic yield than conventional genetic testing and decreased time to genetic diagnosis.

ksfr

m b

Dysmorphisms

Congenital Anomalies

Minor and Major Anomalies

minor anomaly: an unusual anatomic feature that is of no serious medical or cosmetic consequence to

the patient

• major anomaly: anomaly that creates significant medical, surgical, or cosmetic problems for the patient

Mechanism for Anomalies

• malformation: results from an intrinsically abnormal developmental process (e.g polydactyly)

• disruption: results from the extrinsic breakdown of, or interference with, an originally normal

developmental process (e g amniotic band disruption sequence)

• deformation: alteration of the final form of a structure by mechanical forces (e.g Potter deformation

sequence)

• dysplasia: abnormal development that results in abnormal organization of cells into tissues (e.g bone

dysplasia)

Multiple Anomalies

• association: non-random occurrence of multiple independent anomalies that appear together more

than would be predicted by chance but are not known to have a single etiology (e.g VACTERL)

• sequence: related anomalies that come from a single initial major anomaly or precipitating factor that

changes the development of other surrounding or related tissues or structures (e.g Potter sequence or

Pierre-Robin sequence)

• syndrome: a pattern of anomalies that occur together and are known or thought to have a single cause

(e.g Down syndrome)

Approach to the Dysmorphic Child

• congenital abnormalities are the most common cause of infant death in developed countries

General Approach to the Dysmorphic Child

• Are the anomalies major or minor?

• What is the mechanism underlying the anomaly?

• Do the anomalies fit as part of an association, sequence, or syndrome?

History

• prenatal/obstetrical history (see Obstetrics, OB4) with particular attention to potential teratogenic

exposures, developmental history (see Pediatrics, P22), and past medical history

• complete 3 generation family pedigree: health history, consanguinity, stillbirths, neonatal deaths,

specific illnesses, intellectual disability, multiple miscarriages, ethnicity

± esophageal atresia

R Renal anomalies

L Limb anomalies

Face: gestalt

Skull: contour and symmetry

Hair: texture, pattern Eyes: distance apart, brows, lashes,

folds, creases, coloboma, fundus

Neck: webbed, redundant nuchal skin Thorax: shape, size, nipple spacing Genitalia: ambiguous

Ears: structure, size,

placement, rotation

Nose: nasal bridge, nostrils

Philtrum: length, shape

Mouth: lips, palate, tongue, teeth

Limbs: proportions, amputations

Spine: scoliosis, kyphosis

Skin: hair tufts, sacral

dimples, sinus

Hands and Feet: creases,

structure, nails

Growth parameters (head circumference, height, weight)

Chin: size, position

Syndromes and Diseases

Investigations

• screening for TORCH infections

• serial photographs if child is older

• x-rays for bony abnormalities

• cytogenetic studies

■ karyotype if recognized aneuploidy syndrome

■ chromosomal microarray analysis (array comparative genomic hybridization) if developmental

delay OR two or more congenital anomalies

■ FISH if aneuploidy syndrome (e.g trisomy 13, 18 or 21) suspected

• biochemistry: various biochemical profiles, specific enzyme assays

• single gene testing, multi-gene panel testing

Management

• prenatal counselling and assessing risk of recurrence

• referral for specialized pediatric or genetic care for symptomatic management

• specific treatments are available for certain metabolic disorders and genetic syndromes

■ metabolic disorders: enzyme replacement therapy, substrate reduction therapy, etc (e.g low-protein

diet in PKU patients)

■ genetic syndromes: e.g mTOR inhibitors in tuberous sclerosis

Syndromes and Diseases

Large Genomic Changes

Table 1 Trisomy Chromosomal Syndromes

Most common abnormality of autosomal chromosomes

Rises with advanced maternal age from 1:1,500 at age 20

to 1:20 by age 45

1:6,000 live births

Cranium/Brain Mild microcephaly, flat occiput, 3rd fontanelle,

brachycephaly Microcephaly, prominent occiput Microcephaly, sloping forehead, occipital scalp defect, holoprosencephaly

Eyes Upslanting palpebral fissures, inner epicanthal folds,

speckled iris (Brushfield spots), refractive errors (myopia),

acquired cataracts, nystagmus, strabismus

Microphthalmia, hypotelorism, iris coloboma, retinal anomalies Microphthalmia, corneal abnormalities

Ears Low-set, small, overfolded upper helix frequent AOM,

Facial Features Protruding tongue, large cheeks, low flat nasal bridge,

Skeletal/MSK Short stature

Excess nuchal skin

Joint hyperflexibility (80%) including dysplastic hips,

vertebral anomalies, atlantoaxial instability

Short stature Clenched fist with overlapping digits, hypoplastic nails, clinodactyly, polydactyly

Severe growth retardation Polydactyly, clenched hand

GI Duodenal/esophageal/anal atresia, TEF, Hirschsprung’s

Low IQ, developmental delay, hearing problems

Onset of Alzheimer’s disease in 40s

Seizures, deafness Severe developmental delay

Other Features Transverse palmar crease, clinodactyly, and absent middle

phalanx of the 5th finger

1% lifetime risk of leukemia

Polycythemia

Hypothyroidism

SGA Rocker-bottom feet Single umbilical arteryMidline anomalies: scalp, pituitary, palate,

heart, umbilicus, anus Rocker-bottom feet

Prognosis/

Management Prognosis: long term management per AAP Guidelines (Health Supervision of Children with Down syndrome),

recommend chromosomal analysis, CBC, Echo, yearly

thyroid test, atlanto-occipital x-ray at 2 yr, sleep study,

hearing test, and ophthalmology assessment

13% 1-year survival, 10% ten-year survival Profound intellectual disability in survivors 20% 1-year survival, 13% ten-year survivalProfound intellectual disability in survivors

Check the umbilical cord for 2 arteries and 1 vein The presence of a single umbilical artery may be associated with other congenital anomalies

e om

k

e om

ee

Syndromes and Diseases

Table 2 Common Genetic Disorders Involving the Sex Chromosomes

Genetic anticipation

CGG trinucleotide repeat on X chromosome

measurable by molecular analysis

47,XXY (most common)

Incidence 1:3,600 males, 1:6,000 females

Most common heritable cause of intellectual

disability in boys

1:1,000 live male births Increased risk with advanced maternal age 1:4,000 live female birthsRisk not increased with advanced maternal age

Phenotype Overgrowth: prominent jaw, forehead, and nasal

bridge with long and thin face, large protuberant

ears, macroorchidism, hyperextensibility, and high

Short stature, short webbed neck, low posterior hair line, wide carrying angle

Broad chest, widely spaced nipples Lymphedema of hands and/or feet, cystic hygroma in newborn with polyhydramnios, lung hypoplasia Coarctation of aorta, bicuspid aortic valve Renal and cardiovascular abnormalities, increased risk of HTN

Less severe spectrum with mosaic

IQ and Behaviour Mild to moderate intellectual disability, 20% of

affected males have normal IQ

ADHD and/or autism

Female carriers may show intellectual impairment

Male carriers may demonstrate tremor/ataxia

syndrome in later life

Mild intellectual disability Behavioural or psychiatric disorders – anxiety, shyness, aggressive behaviour, antisocial acts

Mild intellectual disability to normal intelligence

Gonad and

Reproductive

Function

Premutation carrier females at risk of developing

premature ovarian failure Infertility due to hypogonadism/hypospermia Streak ovaries with deficient follicles, infertility, primary amenorrhea, impaired development of

secondary sexual characteristics

Diagnosis/

Prognosis/

Management

Molecular testing of FMR1 gene: overamplification

of the trinucleotide repeat, length of segment

is proportional to severity of clinical phenotype

(genetic anticipation)

Increased risk of germ cell tumours and breast cancer

Management: testosterone in adolescence

Normal life expectancy if no complications Increased risk of X-linked diseases Management: Echo, ECG to screen for cardiac malformation

GH therapy for short stature Estrogen replacement at time of puberty for development of secondary sexual characteristics

Table 3 Other Genetic Syndromes

of chromosome 15, or imprinting defect

Lack of expression of genes

on maternal chromosome 15q11-13 due to deletion

or inactivation or paternal uniparental disomy

Autosomal dominant with variable expression PTPN11 mutation most common cause but multiple genes known

2/3 of children with CHARGE have been found

to have a CHD7 mutation on chromosome 8

common genetic diagnosis

(next to Down syndrome)

High risk for schizophrenia

and other psych disorders

“H 3 O”: Hypotonia and

weakness, Hypogonadism,

obsessive Hyperphagia, Obesity

Short stature, almond-shaped eyes, small hands and feet with tapering of fingers Developmental delay (variable) Hypopigmentation, type 2 DM

Ataxia with severe intellectual disability, seizures, tremulousness, hypotonia Midface hypoplasia, fair hair, uncontrollable laughter

Short stature, webbed neck, triangular facies hypertelorism, low set ears, epicanthal fo ds, ptosis, pectus excavatum Right sided CHD, pulmonary stenosis

Increased risk of hematological cancers, moderate intellectual disability, delayed puberty

Syndromes and Diseases

Table 4 Familial Cancer Syndromes

numerous other cancers

PMS2, EPCAM Colorectal, endometrial, ovarian, renal, pancreatic, liver/biliary duct, stomach, brain, breast

Hereditary Breast and Ovarian

Cancer Syndrome BRCA1, BRCA2 Female: breast, ovarian, pancreaticMale: prostate, breast, pancreatic

NF

astrocytoma

Single Gene Disorders

CYSTIC FIBROSIS

• see Respirology, R12 and Pediatrics, P82

SICKLE CELL DISEASE

• one type of muscular dystrophy characterized by progressive skeletal and cardiac muscle degeneration

• X-linked recessive: 1/3 spontaneous mutations, 2/3 inherited mutations

• missing structural protein (dystrophin) → muscle fibre fragility → fibre breakdown → necrosis and

regeneration

Clinical Presentation

• proximal muscle weakness by age 3, positive Gower’s sign, waddling gait, toe walking

• pseudohypertrophy of calf muscles (muscle replaced by fat) and wasting of thigh muscles

• decreased reflexes

• non-progressive delayed motor and cognitive development (dysfunctional dystrophin in brain)

• cardiomyopathy

Diagnosis

• molecular genetic studies of dystrophin gene (DMD) (first line)

• family history (pedigree analysis)

• increased CK (50-100x normal) and lactate dehydrogenase

• elevated transaminases

• muscle biopsy, EMG

Management

• supportive (e.g physiotherapy, wheelchairs, braces , prevent obesity

• cardiac health monitoring and early intervention

• bone health monitoring and intervention (vitamin D, bisphosphonates)

• steroids (e.g prednisone or deflazacort)

• surgical (for scoliosis)

• gene therapy trials underway

Complications

• patient usually wheelchair-bound by 12 yr of age

• early flexion contractures, scoliosis, osteopenia of immobility, increased risk of fracture

• death due to pneumonia/respiratory failure or CHF in 2nd-3rd decade

Syndromes and Diseases

Metabolic Diseases

• inherited disorders of metabolism; often autosomal recessive

• infants and older children may present with FTT or developmental delay

• organelle disorders can present with dysmorphism

universal newborn screening in Ontario includes metabolic disorders

Table 5 Metabolic Disorders

Organic and Amino

Acid Disorders Carbohydrate Disorders Fatty Acid Disorders Organelle Disorders

MCAD deficiency Carnitine deficiency MucopolysaccharidosisCongenital disorders of

glycosylation Lysosomal storage diseases:

Hurler’s, Niemann-Pick, Sachs, Gaucher, Fabry, Krabbe

Tay-Clinical

Manifestations Irritability, lethargy, poor feeding

Seizures

Intellectual disability

Vomiting and acidosis

after feeding initiation

Sweet-smelling urine

(MSUD)

Vomiting and acidosis after feeding initiation Growth retardation, FTT

Lethargy, poor feeding Seizures, coma Symptoms triggered by fasting

Liver dysfunction Sudden infant death

Seizures/early-onset severe epilepsy

Chronic encephalopathy Developmental delay Bone crises (Gaucher) Deafness, blindness

Laboratory

Findings Hypoglycemic hyperammonemia,

high anion gap (organic

Elevated free fatty acids

Elevated urine oligosaccharides (oligosaccharidoses) and glycosaminoglycans (mucopolysaccharidoses) Enzyme deficieny

Physical Exam Hypotonia/hypertonia

cramping

Hepatomegaly Hypotonia Dysmorphic facial featuresMacrocephaly (Tay-Sachs,

Hurler’s) Hepatosplenomegaly (Niemann- Pick type A/B/C, not Tay-Sachs) Cherry-red spot on macula (Niemann-Pick type A/B, Tay- Sachs, Gaucher’s) Corneal clouding (Hurler’s) Infantile cataract (Fabry) Peripheral neuropathy (Fabry, Krabbe)

Spasticity

Initial Investigations

• important to send lab studies at initial presentation in order to facilitate immediate diagnosis and

treatment

• check newborn screening results

• electrolytes, ABGs (calculate anion gap, rule out acidosis)

• CBC with differential and smear

• blood glucose (hypoglycemia seen with organic acidemia, fatty acid oxidation defects, and GSDs)

• lactate, ammonium (hyperammonemia with urea cycle defects), plasma Ca2+ and Mg2+

• routine urinalysis: ketonuria must be investigated

• carnitine levels with acylcarnitine profile

• others: urate, urine nitroprusside, plasma amino acid screen, urine organic acids, CSF glycine, free fatty

acids (3-β-hydroxybutyrate ratio >4 in fatty acid oxidation defect)

• storage diseases: urine mucopolysaccharide and oligosaccharide screen

Treatment

• varies according to inborn error of metabolism

• dietary restrictions, supplementation, enzyme replacement therapy, gene therapy, liver transplant, stem

cell transplant

fre

b k

• deficiency of phenylalanine hydroxylase prevents conversion of phenylalanine to tyrosine leading to

build up of toxic metabolites

• mothers who have PKU may have infants with congenital abnormalities

• PKU screening at birth

• dietary restrict on of phenylalanine starting within the first 10 d of life

• duration of dietary restriction controversial – lifelong or until end of puberty; should be resumed

during pregnancy to maintain normal phenylalanine levels

• large neutral amino acid (tyrosine) replacement, BH4 enzyme treatment, phenylalanine lyase treatment

are other options

• elimination of galactose from the diet (e.g dairy, breast milk)

• most infants are fed a soy-based diet

Complications

• increased risk of sepsis, especially E coli

• if the diagnosis is not made at birth, liver and brain damage may become irreversible

References

Amato RSS Nelson’s essentials of pediatrics, 4th ed Philadelphia: WB Saunders, 2002 Human genetics and dysmorphology 129-146.

Blake KD, Prasad C CHARGE syndrome, o phanet J Rare Diseases 2006;1.

Biggar W Duchenne muscular dystrophy Pediatr Rev 2006;27:83-88

Chudley AE, Conry J, Cook JL, et al Fetal alcohol spectrum disorder: Canadian guidelines for diagnosis CMAJ 2005;172(5 Suppl):S1-21.

Elieff, M P., Lopez-Beltran, A., Montironi, R., & Cheng, L (2008) Familial cancer syndromes In Molecular genetic pathology (pp 449-466) Humana Press.

Grati, F R., Malvestiti, F Ferreira, J C., Bajaj, K., Gaetani, E., Agrati, C., & Maggi, F (2014) Fetoplacen al mosaicism: potential implications for false-positive and

false-negative noninvasive prenatal screening results Genetics in Medicine, 16(8), 620-624.

Moeschler JB, Sheve l M Committee on Genetics Comprehensive evaluation of the child with intellectual disability or global developmental delays Pediatrics 2014

Sep;134(3):e903 18 doi:10.1542/peds.2014-1839

Nicholson JF Nelson’s essentials of pediatrics, 4th ed Philadelphia: WB Saunders, 2002 Inborn errors of metabolism 153-178.

Sobel, E , & Lange, K (1996) Descent graphs in pedigree analysis: applications to haplotyping, location scores, and marker-sharing statistics American journal of human

genetics, 58(6), 1323.

Therrell, B L., & Adams, J (2007) Newborn screening in North America Journal of inherited metabolic disease, 30(4), 447-465.

Vissers LE, van Ravenswaaij CM, Admiraal R, et al Mutations in a new member of the chromodomain gene family cause CHARGE syndrome Nat Genet 2004 36:955-957.

Metabolic disease must be ruled out in any newborn who becomes acut ly ill after a period

of normal behaviour and development or with a

Reffamily history of early infant death even if the

newborn screen is negative

bo

ks

e

m b

sfree.

o

Notes _

_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

Syndromes and Diseases

sf

c

Medical Imaging

MI

Mark Barszczyk, Tian Yang (Darren) Liu, Zafir Syed, and Jinhui Yan, chapter editors Sheliza Halani and Taraneh Tofighi, associate editors

Arnav Agarwal and Sukhmani Sodhi, EBM editors

Dr Nasir Jaffer and Dr Eugene Yu, staff editors

Acronyms 2

Imaging Modalities 2

X-Ray Imaging

Ultrasound

Magnetic Resonance Imaging

Positron Emission Tomography Scans

Approach to Abdominal X-Ray

Abdominal Computed Tomography

Approach to Abdominal Computed Tomography

Contrast Studies

Specific Visceral Organ Imaging

“itis” Imaging

Angiography of Gastrointestinal Tract

Genitourinary System and Adrenal 16

Imaging Modalities

X-Ray Imaging

• x-rays, or Röentgen rays, are a form of electromagnetic energy of short wavelength

• as x-ray photons traverse matter, they can be absorbed (a process known as “attenuation”) and/or

scattered

• the density of a structure determines its ability to attenuate or “weaken” the x-ray beam

■ air < fat < water < bone < metal

• structures that have high at enuation (e.g bone) appear white on the resulting images

Plain Films

• x-rays pass through the patient and interact with a detection device to produce a 2-dimensional

projection mage

• structures closer to the film appear sharper and less magnified

• contraindications: pregnancy (relative)

• advantages: inexpensive, non-invasive, readily available, reproducible, fast

• disadvantages: radiation exposure, generally poor at distinguishing soft tissues

Fluoroscopy

• continuous x-rays used for guiding angiographic and interventional procedures, in contrast

examinations of the GI tract, and in the OR for certain surgical procedures (e.g orthopedic, urological)

• on the fluoroscopic image, black and white are reversed so that bone and contrast agents appear dark

and radiolucent structures appear light

• advantages: allows for real-time visualization of structures

• disadvantages: increased radiation dose; however, the use of pulsed fluoroscopy has reduced

fluoroscopy time by 76% and radiation dose by 64% as compared with continuous fluoroscopy

Computed Tomography

• x-ray beam opposite a detector moves in a continuous 360º arc as patient is advanced through the

imaging system

■ subsequent computer assisted reconstruction of anatomical structures from the axial plane

• attenua ion is quantified in Hounsfield units:

■ subsequent computer assisted reconstruction of anatomical structures from the axial plane

■ adjusting the “window width” (range of Hounsfield units displayed) and “window level” (midpoint

value of the window width) can maximally visualize certain anatomical structures (e.g CT chest can

be viewed using “lung”, “soft tissue”, and “bone” settings)

• contraindications: pregnancy (relative) contraindications to contrast agents (e.g allergy, renal failure)

• advantages: delineates surrounding soft tissues, excellent at delineating bones and identifying lung/

liver masses, may be used to guide biopsies, spiral/helical multidetector CT has fast data acquisition and

allows 3D reconstruction, CTA is less invasive than conventional angiography

• disadvantages: high radiation exposure, soft tissue characterization is not as good in comparison

with MRI, IV contrast injection, anxiety of patient when going through scanner, higher cost, and less

available than plain film

AXR abdominal x-ray

BOOP bronchiolitis obliterans

organizing pneumonia

CNS central nervous system

CSF cerebrospinal fluid

CT computed tomography

CTA computed tomographic angiogram

CVD collagen vascular disease

CVP central venous pressure

CXR chest x-ray

DEXA dual-energy x-ray absorptiometry

DMSA dimercaptosuccinic acid

DSA digital subtraction angiography

DTPA diethylene triamine pentaacetic acid DWI diffusion-weighted image ECD ethyl cysteinate dimer ERCP endoscopic retrograde cholangio- pancreatography

FLAIR fluid-attenuated inversion recovery

GI gastrointestinal GPA granulomatosis with polyangiitis HCC hepatocellular carcinoma HIDA hepatobiliary iminodiacetic acid HMPAO hexamethylpropyleneamine oxime HSG hysterosalpingogram IBD inflammatory bowel disease ICV ileocecal valve IPF interstitial pulmonary fibrosis IVP intravenous pyelogram KUB kidneys, ureters, bladder

POCUS point-of-care ultrasound PTA percutaneous transluminal angioplasty PTC percutaneous transhepatic cholangiography

RA right atrium RAIU radioactive iodine uptake

RV right ventricle SPECT single photon emission computed tomography

SVC superior vena cava

TB tuberculosis TNK tenecteplase tPA tissue plasminogen activator TRUS transrectal ultrasound TVUS transvaginal ultrasound U/S ultrasound VCUG voiding cystourethrogram V/Q ventilation/perfusion

LA left atrium

LV left ventricle MAA microaggregated albumin MAG3 mertiatide

MCA middle cerebral artery

MR magnetic resonance MRA magnetic resonance angiogram MRCP magnetic resonance cholangiopancreatography MRI magnetic resonance imaging

MS multiple sclerosis MUGA multiple gated acquisition

PA posteroanterior PBD percutaneous biliary drainage PET positron emission tomography PFT pulmonary function test PICC peripherally-inserted central catheter

Typical Effective Doses from Diagnostic Medical Exposures (in adults)*

Diagnostic Procedure Type Equivalent

Number

of Chest X-Rays

Approximate Equivalent Period of Natural Background Radiation** (~3 mSv/yr) X-Ray

Skull Cervical spine Thoracic spine Lumbar spine Chest (single PA film) Shoulder Mammography Abdomen Hip Pelvis Knee IVU Dual-energy x-ray absorptiometry (without/

with CT) Upper GI series Small bowel series Barium enema

5 10 50 75 1 0.5 20 35 35 30 0.25 150 0.5/2 300 250 400

CT

Head Neck Spine Chest Chest (pulmonary embolism) Cor nary angiography Abd men Pelvis

100 150 300 350 750 800 400 300

8 mo

1 yr

2 yr 2.3 yr

5 yr 5.3 yr 2.7 yr

2 yr

Radionuclide

Brain (18FDG) Bone ( 99m Tc) Thyroid ( 99m Tc) Thyroid (123I) Cardiac rest-stress test ( 99m Tc 1-d) ( 99m Tc 2-d) Lung ventilation (133Xe) Lung perfusion ( 99m Tc) Renal ( 99m Tc) Liver-spleen ( 99m Tc) Bliary tract ( 99m Tc)

705 315 240 95 470 640 25 100

90 165 105 155

4.7 yr 2.1 yr 1.6 yr

free

ee.c

m

Imaging Modalities

Ultrasound

• high-frequency sound waves are transmitted from a transducer and passed through tissues; reflections

of the sound waves are picked up by the transducer and transformed into images

• reflection (or “echo”) occurs when the sound waves pass through tissue interfaces of different acoustic

densities

• structures are described based on their echogenicity; hyperechoic structures appear bright (U/S

reflected) whereas hypoechoic structures appear dark (U/S waves not reflected back but pass through)

• higher U/S frequencies result in greater resolution but greater attenuation (i.e deeper structures more

difficult to visualize)

• artifacts: acoustic shadowing refers to the echo-free area located behind an interface that strongly

reflects (e.g tissue/air) or absorbs (e.g tissue/bone) sound waves; enhancement refers to the increase

in reflection amplitude (i.e increased brightness) from objects that lie below a weakly attenuating

structure (e.g cyst)

• Duplex scan: grey-scale image that utilizes the Doppler effect to visualize the velocity of blood flow past

the transducer

• Colour Doppler: assigns a colour based on the direction of blood flow (i.e red = toward transducer,

blue = away)

• advantages: relatively low cost, non-invasive, no radiation, real time imaging, may be used for guided

biopsies many different imaging planes (axial, sagittal), determines cystic versus solid

• disadvantages: highly operator-dependent, air in bowel may prevent imaging of midline structures in

the abdomen, may be limited by patient habitus, poor for bone evaluation

Magnetic Resonance Imaging

• non-invasive imaging technique that does not use ionizing radiation and able to produce images in

virtually any plane

• patient is placed in a magnetic field; protons (H+) align themselves along the plane of magnetization

due to intrinsic polarity A pulsed radiofrequency beam is subsequently turned on and deflects all the

protons off their aligned axes due to absorption of energy from the radiofrequency beam When the

radiofrequency beam is turned off, the protons return to their pre-excitation axis, giving off the energy

they absorbed This energy is measured with a detector and interpreted by software to generate MR

images

• the MR image reflects the signal intensity picked up by the receiver This signal intensity is dependent

on:

1 hydrogen density: tissues with low hydrogen density (e.g cortical bone, lung) generate little to no

MR signal compared to tissues with high hydrogen density (e.g water)

2 magnetic relaxation times (T1 and T2): reflect quantitative alterations in MR signal strength due to

intrinsic properties of the tissue and its surrounding chemical and physical environment

Table 1 Differences Between Diffusion, T1- and T2-Weighted MR Imaging

Diffusion-Weighted

Imaging Contrast dependent on the molecular motion of water

Decreased diffusion is hyper ntense (bright), whereas increased diffusion is hypointense (dark)

Neuroradiology Sensitive for detection of acute ischemic stroke

and differentiating an acute stroke from other neurologic pathologies

Acute infarction appears hyperintense Abscess collections also show restricted diffusion

T1-Weighted Fluid is hypointense (dark) and

fat is hyperintense (bright) Body soft tissues Often considered an anatomic scan since they provide a reference for functional imaging

T2-Weighted Fluid is hyperintense (bright)

and fat is hypointense (dark) Body soft tiss es Often considered a pathologic scan since they will highlight edematous areas associated with

certain pathologies

Positron Emission Tomography Scans

• non-invasive technique that involves exposure to ionizing radiation (~7 mSv)

• nuclear medicine imaging technique that produces images of functional processes in the body

• current generation models integrate PET and CT technologies into a single imaging device (PET-CT)

that collects both anatomic and functional information during a single acquisition

• positron-producing radioisotopes, such as 18FDG, are chemically incorporated into a metabolically

active molecule (e.g glucose) These are then injected into the patient, travel to the target organ,

and accumulate in tissues of interest As the radioactive substance begins to decay, gamma rays are

produced, and are then detected by the PET scanner

• contraindications: pregnancy

• advantages shows metabolism and physiology of tissues (not only anatomic); in oncology, allows for

diagnosis staging, and restaging; has predictive and prognostic value; can evaluate cardiac viability

• disadvantages: cost, ionizing radiation

Contrast-• Optimal: 0.9% NaCl at 1 ml/kg/hr for 12

hr pre-procedure and 12 hr post-contrast administration

• For same-day procedure: 0.9% NaCl

or NaHCO3 at 3 ml/kg/hr for 1-3 hr pre-procedure and for 6 hr post-contrast administration

Remember that water is “white” on T2 as

“World War II”

Contraindications to IV Contrast MADD Failure

Multiple myeloma Adverse reaction previously DM

Dehydration Failure (renal severe heart)

book

fre

me ook

Chest Imaging

Contrast Enhancement

Table 2 Contrast Agents

X-Ray/CT 1 Barium (oral or rectal) Radio-opaque substance

that helps to delineate intraluminal anatomy; may demonstrate patency, lumen integrity, or large filling defects

Previous adverse reaction

to contrast; barium enema is contraindicated

in toxic megacolon, acute colitis, and suspected perforation

2 Iodine (IV injection) Delineates intraluminal

anatomy; may demonstrate patency, lumen integrity, or large filling defects; under fluoroscopy, may also give information on function of

an organ

Risk of nephrogenic systemic fibrosis in patients with end-stage renal disease

Previous adverse reaction

to contrast, renal failure,

DM, pregnancy, multiple myeloma, severe heart failure and dehydration eGFR <60 may require preventative measures and follow-up

(IV injection) Shortens T1 relaxation time, thereby increasing

signal intensity in weighted sequences;

T1-gadolinium has some effect on T2-relaxation time; highlights highly vascular structures (e.g

tumours)

Risk of nephrogenic systemic fibrosis in patients with end-stage renal disease

Previous adverse reaction to contrast or if end-stage renal disease (relative contraindication)

(IV injection) Since gas is highly echogenic, the

microbubbles allow for echo-enhancement of a tissue

Contraindicated in individuals with right- to-left cardiac shunts

or people with known hypersensitivity reactions

Chest Imaging

Chest X-Ray

Standard Views

• PA: anterior chest against film plate to minimize magnification of the heart size

• lateral: better visualization of retrocardiac space and thoracic spine (more sensitive at picking up pleural

effusions)

■ helps localize lesions when combined with PA view

• AP: for bedridden patients (generally a lower quality film than PA because of enlarged cardiac

silhouette)

• lateral decubitus: to assess for pleural effusion and pneumothorax in bedridden patients; however,

POCUS can also be utilized for both of these purposes

• lordotic: angled beam allowing better visualization of apices normally obscured by the clavicles and

• markers: right and/or left

• technique: view (e.g PA, AP, lateral), supine or erect

• indications for the study

• comparison: date of previous study for comparison (if available)

• quality of film: inspiration (6th anterior and 10th posterior ribs should be visible), penetration (thoracic

spine should be visible) and rotation (clavicles vs spinous process)

Lordotic Position Anterior-posterior Position Lateral Decubitus Position ©Bonnie Tang 2012

Chest Imaging

Analysis

• tubes and lines: check position and be alert for pneumothorax or pneumomediastinum

• soft tissues: neck, axillae, pectoral muscles, breasts/nipples, chest wall

■ nipple markers can help identify nipples (may mimic lung nodules)

■ amount of soft tissue, presence of masses and air (subcutaneous emphysema)

• abdomen (see Abdominal Imaging, MI10)

■ free air under the diaphragm, air-fluid levels, distention in small and large bowels

■ herniation of abdominal contents (i.e diaphragmatic hernia)

• bones: C-spine, thoracic spine, shoulders ribs, sternum, clavicles

■ lytic and blastic lesions and fractures

• mediastinum: trachea, heart, great vessels

■ cardiomegaly (cardiothoracic ratio >0.5), tracheal shift, tortuous aorta, widened mediastinum

• hila: pulmonary vessels, mainstem and segmental bronchi, lymph nodes

• lungs: lung parenchyma, pleura, diaphragm

■ comment on abnormal lung opacity, pleural effusions or thickening

■ right hemidiaphragm usually higher than left due to liver

■ right vs left hemidiaphragm can be discerned on lateral CXR due to heart resting directly on left

hemidiaphragm

• please refer to Toronto Notes website for supplementary material on how to approach a CXR

Anatomy

Localizing Lesions for Parenchymal Lung Disease

• silhouette sign: when two objects of the same radiolucency contact each other, they become

indistinguishable on imaging and result in the loss of normal interfaces It can be used to identify

lung pathology (consolidation, atelectasis, mass) and localize disease to specific lung segments The

silhouette sign is not only used in the chest, but can also be an aid to interpreting imaging studies

throughout the body

• spine sign: on lateral films, vertebral bodies should appear progressively radiolucent as one moves down

the thoracic vertebral column; if they appear more radio-opaque, it is an indication of pathology (e.g

consolidation in overlying left lower lobe)

• air bronchogram: branching pattern of air-filled bronchi on a background of fluid-filled airspaces

Table 3 Localization Using the Silhouette Sign

SVC/right superior mediastinum RUL

Aortic knob/left superior mediastinum LUL

Figure 2 Location of fissures, mediastinal structures, and bony landmarks on CXR

Chest X-Ray Interpretation Basics ABCDEF

AP, PA or other view Body position/rotation Confirm name Date Exposure/quality Films for comparison Analysis ABCDEF Airways and hilar Adenopathy Bones and Breast shadows Cardiac silhouette and Costophrenic angle Diaphragm and Digestive tract Edges of pleura

Fields (lung fie ds)

Legend

a1 anterior 1st rib a2 anterior 2nd rib

aa aort c arch apw aorto-pulmonary window

as anterior airspace

ca carina

cl clavicle

co coracoid process cpa costophrenic angle

di diaphragm

g gastric bubble ivc inferior vena cava

la left atrium lbr left mainstem bronchus lpa left pulmonary artery

lv left ventricle

mf major fissure

mi minor fissure p3 posterior 3rd rib p4 posterior 4th rib

pa main pulmonary artery

ra right atrium rbr right mainstem bronchus rpa right pulmonary artery

rv right ventricle

sc scapula

sp spinous process

st sternum svc superior vena cava

rpa rbr lbr mf mi

ivc di cpa

di ivc

cpa di

lpa pa

tr

rpa rbr

svc apw

mi

cpa

sp a1

ra

rv lvvb

g

vb rv

lv la

Chest Imaging

Figure 3 Location of lobes of the lung

Computed Tomography Chest

Approach to CT Chest

• soft tissue window

■ thyroid, chest wall, pleura

■ hea t: chambers, coronary artery calcifications, pericardium

■ vessels: aorta, pulmonary artery, smaller vasculature

■ lymph nodes: mediastinal, axillary

bone window

■ vertebrae, sternum, manubrium, ribs: fractures, lytic lesions, sclerosis

• lung window

■ trachea: patency, secretions

■ bronchial trees: anatomic variants, mucus plugs, airway collapse

■ lung parenchyma: fissures, nodules, fibrosis/interstitial changes

■ pleural space: effusions

• please refer to Toronto Notes website for supplementary material on how to approach a CT chest

Table 4 Types of CT Chest

Standard Scans full lung very quickly

(<1 min) Poor at evaluating diffuse disease ± CXR abnormalityPleural and mediastinal abnormality

Lung cancer staging Follow-up metastases Empyema vs abscess

High

Resolution Thinner slices provide high definition of lung parenchyma Only 5-10% lung is sampled No HemoptysisDiffuse lung disease (e g sarcoidosis,

hypersensitivity pneumonitis, pneumoconiosis) Pulmonary fibrosis Normal CXR but abnormal PFTs Characterize solitary pulmonary nodule

Follow-up infections, lung transplant, metastases

CTA Iodinated contrast highlights

asculature Contrast can cause severe allergic reaction and is

nephrotoxic

Aortic aneurysms Aortic dissection

■ increased opacity of involved segment/lobe, vascular crowding, silhouette sign, air bronchograms

■ volume loss: fissure deviation, hilar/mediastinal displacement, diaphragm elevation

■ compensatory hyperinflation of remaining normal lung

• differential diagnosis

■ obstructive (most common): air distal to obstruction is reabsorbed causing alveolar collapse

◆ post-surgical, endobronchial lesion, foreign body, inflammation (granulomatous infections,

pneumoconiosis, sarcoidosis, radiation injury), or mucous plug (cystic fibrosis)

■ compressive

■ tumour bulla, effusion, enlarged heart, lymphadenopathy

■ traction (cicatrization): due to scarring, which distorts alveoli and contracts the lung

■ adhesive: due to lack of surfactant

◆ hyaline membrane disease, prematurity

RUL: Right Upper Lobe; RML: Right Middle Lobe; RLL: Right Lower Lobe; LUL: Left Upper Lobe; LLL: Left Lower Lobe

RUL

RUL RML RML

RLL RLL

LUL LLL

Front AP Right-Lateral

RUL RML

RLL

LUL

LUL LLL

Back AP Left-Lateral

LLL

Figure 4 CT thorax windows

Soft Tissue Window

• Fluid (e.g pulmonary edema)

• Blood (e.g pulmonary hemorrhage)

• Cells (e.g bronchioalveolar carcinoma, lymphoma)

• Protein (e.g alveolar proteinosis)

Figure 6 Air bronchograms in right lung

eb o

Chest Imaging

■ passive (relaxation): a result of air or fluid in the pleural space

◆ pleural effusion, pneumothorax

• management: in the absence of a known etiology, persisting atelectasis must be investigated (i.e CT

thorax) to rule out a bronchogenic carcinoma

Consolidation

• pathogenesis: fluid (water, blood), inflammatory exudates, protein, or tumour in alveoli

• findings

■ air bronchograms: lucent branching bronchi visible through opacification

■ airspace nodules: fluffy, patchy, poorly defined margins with later tendency to coalesce, may take on

lobar or segmental distribution

■ silhouette sign

• differential diagnosis

■ fluid: pulmonary edema, blood (trauma, vasculitis, bleeding disorder, pulmonary infarct)

■ inflammatory exudates: bacterial infections, TB, allergic hypersensitivity alveolitis, BOOP, allergic

bronchopulmonary aspergillosis, aspiration, sarcoidosis

■ protein: pulmonary alveolar proteinosis

■ tumour: bronchoalveolar carcinoma, lymphoma

• management: varies depending on the pattern of consolidation, which can suggest different etiologies;

should also be done in the context of clinical picture

Interstitial Disease

• pathogenesis: pathological process involving the interlobular connective tissue (i.e “scaffolding of the

lung”)

• findings

■ linear: fine lines caused by thickened connective tissue septae

◆ Kerley A: long thin lines in upper lobes

◆ Kerley B: short horizontal lines extending from lateral lung margin

◆ Kerley C: diffuse linear pattern throughout lung

◆ seen in pulmonary edema, lymphangitic carcinomatosis, and atypical interstitial pneumonias

■ nodular: 1-5 mm well-defined nodules distributed evenly throughout lung

◆ seen in malignancy, pneumoconiosis, and granulomatous disease (e.g sarcoidosis, miliary TB)

■ reticular (honeycomb): parenchyma replaced by thin-walled cysts suggesting extensive destruction

of pulmonary tissue and fibrosis

◆ seen in IPF, asbestosis, and CVD

◆ watch for pneumothorax as a complication

■ reticulonodular: combination of reticular and nodular patterns

■ may also see signs of airspace disease (atelectasis, consolidation)

• differential diagnosis

■ occupational/environmental exposure

◆ inorganic: asbestosis, coal miner’s pneumoconiosis, silicosis, berylliosis, talc pneumoconiosis

◆ organic: hypersensitivity pneumonitis, bird fancier’s lung, farmer’s lung (mouldy hay), and other

organic dust

■ autoimmune: CVD (e.g rheumatoid arthritis, scleroderma, SLE, polymyositis, mixed connective

tissue disease), IBD, celiac disease, vasculitis

■ drug-related: antibiotics (cephalosporins, nitrofurantoin), NSAIDs, phenytoin, carbamazepine,

fluoxetine, amiodarone, chemotherapy (e.g methotrexate), heroin, cocaine, methadone

■ infections: non-tuberculous mycobacteria, certain fungal infections

■ idiopathic: hypersensitivity pneumonitis, IPF, BOOP

■ for Causes of Interstitial Lung Disease Classified by Distribution see Respirology, R13

■ management: high-resolution CT thorax and biopsy

Pulmonary Nodule

• findings: round opacity ± silhouette sign

■ note: do not mistake nipple shadows for nodules; if in doubt, repeat CXR with nipple markers

• differential diagnosis

■ extrapulmonary density: nipple, skin lesion, electrode, pleural mass, bony lesion

■ solitary nodule

◆ tumour: carcinoma, hamartoma, metastasis, bronchial adenoma

◆ inflammation: histoplasmoma, tuberculoma, coccidioidomycosis

◆ vascular: AV fistula, pulmonary varix (dilated pulmonary vein), infarct, embolism

■ multiple nodules: metastases, abscess, granulomatous lung disease (TB, fungal, sarcoid, rheumatoid

nodules, silicosis, GPA)

• management: clinical information and CT appearance determine level of suspicion of malignancy

■ if high probability of malignancy, invasive testing (fine needle aspiration, transbronchial/

transthoracic biopsy) is indicated

■ if low probability of malignancy, repeat CXR or CT in 1-3 mo and then every 6 mo for 2 yr; if no

change, then >99% chance benign

DDx of Interstitial Lung Disease FASSTEN (upper lung disease) Farmer’s lung (hypersensitivity pneumonitis) Ankylosing spondylitis

Sarcoidosis Silicosis TB Eosinophilic granuloma (Langerhans cell

histiocytosis)

Neurofibromatosis BAD RASH (lower lung disease) BOOP

Asbestos Drugs (nitrofurantoin, hydralazine, isoniazid,

amiodarone, many chemotherapy drugs)

Rheumatological disease Aspiration

Scleroderma Hamman Rich (IPF) and idiopathic pulmonary

Oncological Lymphangioleiomyomatosis Environmental, occupational Sarcoidosis

Figure 9 Interstitial disease: medium reticular pattern

bo

ksfre

m b

sf

c

booksfree.co

m bo

Chest Imaging

Table 5 Characteristics of Benign and Malignant Pulmonary Nodules

Other Features Cavitation, collapse, adenopathy, pleural effusion, lytic bone

lesions, smoking history

Cavitation Yes, especially with wall thickness >15 mm, eccentric cavity, and

Pulmonary Vascular Abnormalities

Pulmonary Edema

• pathogenesis: fluid accumulation in the airspaces of the lungs

• findings

■ vascular redistribution/enlargement, cephalization, pleural effusion, cardiomegaly (may be present

in cardiogenic edema and fluid overloaded states)

■ fluid initially collects in interstitium

◆ loss of definition of pulmonary vasculature

◆ peribronchial cuffing

◆ Kerley B lines

◆ reticulonodular pattern

◆ thickening of interlobar fissures

■ as pulmonary edema progresses, fluid begins to collect in alveoli causing diffuse airspace disease

often in a “bat wing” or “butterfly” pattern in perihilar regions with tendency to spare the outermost

lung fields

• differential diagnosis: cardiogenic (e.g CHF), renal failure, volume overload, non-cardiogenic (e.g

ARDS)

Pulmonary Embolism

• pathogenesis: arterial blockage in the lungs due to emboli from pelvic or leg veins, rarely from PICC

lines, ports, air, fat, or amniotic fluid (difficult to diagnose on imaging except by combination of clinical

history and CXR and CT findings of ARDS)

• findings

■ CXR: Westermark sign (localized pulmonary oligemia), Hampton’s hump (triangular peripheral

infarct), enlarged right ventricle and right atrium, atelectasis, pleural effusion, and rarely pulmonary

edema

■ definitive imaging study: CT pulmonary angiography to look for filling defect in contrast-filled

pulmonary arteries (emboli can be seen up to 4th order arterial branching)

■ V/Q scan: not a diagnostic study

Pleural Abnormalities

Pleural Effusion

Table 6 Sensitivity of Plain Film Views for Pleural Effusion

X Ray Projection Minimum Volume to Visualize

Lateral decubitus 25 mL: most sensitive

Upright lateral 50 mL: meniscus seen in the posterior costophrenic sulcus

• a horizontal fluid level is seen only in a hydropneumothorax (i.e both fluid and air within pleural

cavity)

• effusion may exert mass effect, shift trachea and mediastinum to opposite side, or cause atelectasis of

adjacent lung

• U/S is superior to plain film for detection of small effusions and may also aid in thoracentesis, and

POCUS is now standard of care in acute situations

• fluid level >1 cm on lateral decubitus film is indication to perform thoracentesis

Figure 10 Pulmonary nodule:

bronchogenic carcinoma

Figu e 11 Peribronchial cuffing

Figure 12 Pleural effusion in lateral view

■ upright chest film allows visualization of visceral pleura as curvilinear line paralleling chest wall

separating partially collapsed lung from pleural air

■ more obvious on expiratory (increased contrast between lung and air) or lateral decubitus films (air

collects superiorly)

■ more difficult to detect on supine film; look for the “deep (costophrenic) sulcus” sign, double

diaphragm” sign (dome and anterior portions of diaphragm outlined by lung and pleural air,

respectively), hyperlucent hemithorax, sharpening of adjacent mediastinal structures

■ mediastinal shift may occur if tension pneumothorax

• differential diagnosis: spontaneous (tall and thin males, smokers), iatrogenic (lung biopsy, ventilation,

CVP line insertion), trauma (associated with rib fractures), emphysema, malignancy, honeycomb lung

• management: needle decompression or chest tube insertion, repeat CXR to ensure resolution

Asbestos

• asbestos exposure may cause various pleural abnormalities including benign plaques (most common;

these may calcify), diffuse pleural fibrosis, effusion, and malignant mesothelioma

Mediastinal Abnormalities

Mediastinal Mass

the mediastinum is divided into four compartments; this provides an approach to the differential

diagnosis of a mediastinal mass

• anterior border formed by the sternum and posterior border by the heart and great vessels

■ 4 Ts: see sidebar

■ cardiophrenic angle mass differential: thymic cyst, epicardial fat pad, foramen of Morgagni hernia

• middle border (extending behind anterior mediastinum to a line 1 cm posterior to the anterior border

of the thoracic vertebral bodies)

■ esophageal carcinoma, esophageal duplication cyst, metastatic disease, lymphadenopathy (all

causes), hiatus hernia, bronchogenic cyst

• posterior border (posterior to the middle line described above)

■ neurogenic tumour (e.g neurofibroma, schwannoma), multiple myeloma, pheochromocytoma,

neurenteric cyst, thoracic duct cyst, lateral meningocele, Bochdalek hernia, extramedullary

hematopoiesis

• superior boundaries (superiorly by thoracic inlet, inferiorly by plane of the sternal angle, anteriorly by

manubrium, posteriorly by T1-T4, laterally by pleura)

• in addition, any compartment may give rise to lymphoma, lung cancer, aortic aneurysm or other

vascular abnormalities, abscess, or hematoma

Enlarged Cardiac Silhouette

• heart borders

■ on PA view, right heart border is formed by right atrium; left heart border is formed by left atrium

and left ventricle

■ on lateral view, anterior heart border is formed by right ventricle; posterior border is formed by left

atrium (superior to left ventricle) and left ventricle

• cardiothoracic ratio = greatest transverse dimension of the central shadow relative to the greatest

transverse dimension of the thoracic cavity

■ using a good quality erect PA chest film in adults, cardiothoracic ratio of >0.5 is abnormal

• ratio <0.5 does not exclude enlargement (e.g cardiomegaly + concomitant hyperinflation)

• pericardial effusion: globular heart with loss of indentations on left mediastinal border

• RA enlargement: increase in curvature of right heart border and enlargement of SVC

• LA enlargement: straightening of left heart border; increased opacity of lower right side of

cardiovascular shadow (double heart border); elevation of left main bronchus (specifically, the upper

lobe bronchus on the lateral film), distance between left main bronchus and “double” heart border >7

cm, splayed carina (late sign)

• RV enlargement: elevation of cardiac apex from diaphragm; anterior enlargement leading to loss of

retrosternal air space on lateral; increased contact of right ventricle against sternum

• LV enlargement: rounding of the cardiac apex; displacement of left cardiac boarder leftward, inferiorly,

elevation

Depressed Hemidiaphragm Suggests TALC

Tumour Asthma Large pleu al effusion COPD

DDx Anterior Mediastinal Mass

4 Ts Thyroid Thymic neoplasm Teratoma Terrible lymphoma

Figure 14 Lateral CXR showing four mediastinal compartments

oo

fr

m boo

fr

c

m b

m

Abdominal Imaging

Tubes, Lines, and Catheters

• ensure appropriate placement and assess potential complications of lines and tubes

• avo d mistaking a line/tube for pathology (e.g oxygen rebreather mask for pneumothoraces)

Central Venous Catheter

• used for fluid and medication administration, vascular access for hemodialysis, and CVP monitoring

• tip must be located proximal to right atrium to prevent inducing arrhythmias or perforating wall of

atrium

■ if monitoring CVP, catheter tip must be proximal to venous valves

• tip of well-positioned central venous catheter projects over silhouette of SVC in a zone demarcated

superiorly by the anterior first rib end and clavicle, and inferiorly by top of RA

• course should parallel course of SVC; if appears to bend as it approaches wall of SVC or appears

perpendicular, catheter may damage and ultimately perforate wall of SVC

• complications: pneumothorax, bleeding (mediastinal, pleural), air embolism

Endotracheal Tube

• frontal chest film: tube projects over trachea and shallow oblique or lateral chest radiograph will help

determine position in 3 dimensions

• progressive gaseous distention of stomach on repeat imaging is concerning for esophageal intubation

• tip should be located 4 cm above tracheal carina (avoids bronchus intubation and vocal cord irritation)

• maximum inflation diameter <3 cm to avoid necrosis of tracheal mucosa and rupture; ensure diameter

of balloon is less than tracheal diameter above and below balloon

• complications: aspiration (parenchymal opacities), pharyngeal perforation (subcutaneous emphysema,

pneumomediastinum, mediastinitis)

Nasogastric Tube

• tip and sideport should be positioned distal to esophagogastric junction and proximal to gastric pylorus

• radiographic confirmation of tube is mandatory because clinical techniques for assessing tip position

if tip is located more distally, increased risk of prolonged pulmonary artery occlusion resulting in

pulmonary infarction or, rarely, pulmonary artery rupture

• complications: pneumothorax, bleeding (mediastinal, pleural), air embolism

Chest Tube

• in dorsal and caudal portion of pleural space to evacuate fluid

• in ventral and cephalad portions of pleural space to evacuate pneumothoraces

• tube may lie in fissure as long as functioning

• complications: lung perforation (mediastinal opacities)

■ chronic symptoms: constipation, calcifications (gallstones, renal stones, urinary bladder stones, etc.)

■ not useful in: GI bleeds, chronic anemia, vague GI symptoms

Anatomy

• abdomen divided into 2 cavities

■ peritoneal cavity: lined by peritoneum that wraps around most of the bowel, the spleen, and most of

the liver; forms a recess lateral to both the ascending and descending colon (paracolic gutters)

■ retroperitoneal cavity: contains several organs situated posterior to the peritoneal cavity; the contour

of these can often be seen on radiographs

Figure 15 CXR showing well-positioned central venous catheter

ee.com

co

Abdominal maging

Table 7 Differentiating Small and Large Bowel

Mucosal Folds Uninterrupted valvulae conniventes (or plicae

circularis) Interrupted haustra extend only partway across lumen

Approach to Abdominal X-Ray

• mnemonic: “Free ABDO”

• “Free”: free air and fluid

■ free fluid

◆ small amounts of fluid: increased distance between lateral fat stripes and adjacent colon may

indicate free peritoneal fluid in the paracolic gutters

◆ large amounts of fluid: diffuse increased opacification on supine film; bowel floats to centre of

anterior abdominal wall

◆ ascites and blood (hemoperitoneum) are the same density on the radiograph, and therefore,

cannot be differentiated

◆ free intraperitoneal air suggests rupture of a hollow viscus (anterior duodenum, transverse

colon), penetrating trauma, or recent (<7 d) surgery

• “A”: air in the bowel (can be normal, ileus, or obstruction)

■ volvulus – twisting of the bowel upon itself; from most to least common:

◆ sigmoid: “coffee bean” sign (massively dilated sigmoid projects to right or mid-upper abdomen)

with proximal dilation

◆ cecal: massively dilated bowel loop projecting to left or mid-upper abdomen with small bowel

dilation

◆ gastric: rare

◆ transverse colon: rare (usually young individuals)

◆ small bowel: “corkscrew sign” (rarely diagnosed on plain films, seen best on CT)

■ toxic megacolon

◆ manifestation of fulminant colitis

◆ extreme dilatation of colon (>6.5 cm) with mucosal changes (e.g foci of edema, ulceration,

pseudopolyps), loss of normal haustral pattern

• “B”: bowel wall thickening

■ increased soft tissue density in bowel wall, thumb-like indentations in bowel wall

(“thumb-printing”), or a picket-fence appearance of the valvulae conniventes (“stacked coin” appearance)

■ may be seen in IBD, infection, ischemia, hypoproteinemic states, and submucosal hemorrhage

• “D”: densities

■ bones: look for gross abnormalities of lower ribs, vertebral column, and bony pelvis

■ abnormal calcifications: approach by location

◆ RUQ: renal stone, adrenal calcification, gallstone, porcelain gallbladder

◆ RLQ: ureteral stone appendicolith, gallstone ileus

◆ LUQ: renal stone adrenal calcification, tail of pancreas

◆ LLQ: ureteral stone

◆ central: aorta/aortic aneurysm, pancreas, lymph nodes

◆ pelvis: phleboliths (i.e calcified veins), uterine fibroids, bladder stones

• “O”: organs

■ kidney, liver, gallbladder, spleen, pancreas, urinary bladder, psoas shadow

■ outlines can occasionally be identified because they are surrounded by more lucent fat, but all are

best visualized with other imaging modalities (CT, MRI)

Figure 16 Normal AXRs: (left) supine anteroposterior AXR, (m ddle) upright anteroposterior AXR, and (right)

left lateral decubitus AXR

3-6-9 Rule of Dilation

Small bowel (>3 cm) Large bowel (>6 cm) Cecum (>9 cm)

Abdominal Imaging

Table 8 Abnormal Air on Abdominal X-Ray

Supine film: gas outlines of structures not normally seen:

Inner and outer bowel wall (Rigler’s sign) Falciform ligament

Peritoneal cavity (“football” sign)

Perforated viscus Post-operative (up to 10 d to be resorbed)

Retroperitoneal Gas outlining retroperitoneal structures allowing

increased visualization:

Psoas shadows Renal shadows

Perforation of retroperitoneal segments of bowel:

duodenal ulcer, post-colonoscopy

2 Rounded (cystoides type)

1 Linear: ischemia, necrotizing enterocolitis

2 Rounded/cystoides (generally benign):

prima y (idiopathic), secondary to COPD

Intraluminal Dilated loops of bowel, air-fluid levels Adynamic (paralytic) ileus, mechanical bowel

obstruction

Loculated Mottled, localized in abnormal position without normal

ulcer, cholangitis, emphysematous cholecystitis

Portal Venous Air peripherally over liver in branching pattern Bowel ischemia/infarction

Table 9 Adynamic Ileus vs Mechanical Obstruction

Air-Fluid Levels

(erect and left lateral

decubitus films only)

Same level in the same single loop Multiple air fluid levels giving “step ladder”

appearance, dynamic (indicating peristalsis present), “string of pearls” (row of small gas accumulations in the dilated valvulae conniventes)

Distribution of Bowel Gas Air throughout GI tract is generalized or

No air distal to obstructed segment

“Hairpin” (180°) turns in bowel

Abdominal Computed Tomography

• indications for plain CT: renal colic, hemorrhage

• indications for CT with contrast

■ IV contrast given immediately before or during CT to allow identification of arteries and veins

◆ portal venous phase: indicated for majority of cases

◆ biphasic (arterial and portal venous phases): liver, pancreas, bile duct tumours

◆ caution: contrast allergy (may premedicate with steroids and antihistamine)

◆ contraindication: impaired renal function (based on eGFR)

■ oral contrast: barium or water-soluble (water soluble if suspected perforation) given in most cases to

demarcate GI tract

■ rectal contrast: given for investigation of colonic lesions

Approach to Abdominal Computed Tomography

• look through all images in gestalt fashion to identify any obvious abnormalities

• look at each organ/structure individually from top to bottom, evaluating size and shape of each area of

increased or decreased density

• evaluate the following:

■ soft tissue window

◆ liver, gallbladder, spleen and pancreas

◆ adrenals, kidneys, ureters, and bladder

◆ stomach, duodenum, small bowel mesentery, and colon/appendix

◆ retroperitoneum: aorta, vena cava, and mesenteric vessels; look for adenopathy in vicinity of

vessels

◆ peritoneal cavity for fluid or masses

◆ abdominal wall and adjacent soft tissue

■ lung window

◆ visible lung (bases)

■ bone window

◆ vertebrae, spinal cord, and bony pelvis

Biliary vs Portal Venous Air

“Go with the flow”: air follows the flow of bile

or portal venous blood Biliary air is most prominent centrally over the liver

Portal venous air is most prominent peripherally

Colorectal Cancer: CT Colonography and Colonoscopy for Detection-Systematic Review and Meta-Analysis

Radiology 2011;259:393-405

Purpose: To assess the sensitivity of computed

tomography (CT) colonography and optical colonoscopy (OC) for colorectal cancer (CRC) detection.

Methods: Systematic review and meta-analysis

of diagnostic studies evaluating CT colonography detection of CRC based on a priori eligibility criteria,

in particular requiring both OC and histological confirmation of disease Studies that also assessed true-positive and false-negative diagnoses with OC were used to calculate OC sensitivity Sensitivity of CTC and OC for CRC was the main outcome.

Results: 49 studies on 11,151 patients undergoing

diagnostic study for detection of CRC were included CTC has a sensitivity of 96.1% (95% CI 93.8%, 97.7%) and OC has a sensitivity of 94.7% (95% CI 90.4%, 97.2%) for the detection of CRC.

Conclusion: CTC is highly sensitive for the

detection of CRC and may be a better modality for the initial investigation of suspected CRC, assuming reasonable specificity.

com

m oo

Abdominal maging

Figure 17 Axial abdominal computed tomography

CT and Bowel Obstruction

• cause of bowel obstruction rarely found on plain films; CT is best choice for imaging

• the “3 6,9” rule is a very useful guide to determining when the bowel is dilated; the maximum diameter

of he bowel is 3 cm for small bowel, 6 cm for large bowel, and 9 cm for cecum; this can also be seful

to distinguish small and large bowel, and to assess for ‘impending’ cecal perforation (e.g post-untreated

Ogilvie’s syndrome)

• closed-loop obstruction: an obstruction in two locations (usually small bowel) creating a loop of bowel

segment obstructed both proximally and distally; complications (e.g ischemia, perforation, necrosis)

may occur quickly

CT Colonography (virtual colonoscopy)

• emerging imaging technique for evaluation of intraluminal colonic masses (i e polyps, tumours)

• two CT scans of the abdomen (prone and supine) after the instillation of carbon dioxide into a prepped

colon

• computer reconstruction of 2D CT images into a 3D intraluminal view of the colon

• lesions seen on 3D images correlated with 2D axial images

• indications: surveillance in low-risk patients, incomplete colonoscopy, staging of obstructing colonic

lesions

Contrast Studies

Table 10 Types of Contrast Studies

Cine

Esophagogram Cervical esophagus Contrast agent swallowedRecorded for later playback

and analysis

Dysphagia, swallowing incoordination, recurrent aspiration, post-operative cleft palate repair

Aspiration, webs (partial occlusion), Zenker’s diverticulum, cricopharyngeal bar, laryngeal tumour

Barium Swallow Thoracic esophagus Contrast agent swallowed

under fluoroscopy, selective images captured

Dysphagia, rule out GERD, post-esophageal surgery

Achalasia, hiatus hernia, esophagitis, cancer, esophageal tear

Upper GI Series Thoracic esophagus,

stomach, and

duodenum

Double contrast study:

1 Barium to coat mucosa, then

2 Gas pills for distention Patient NPO after midnight

Dyspepsia, investigate possible upper GI bleed, weight loss/anemia, post-gastric surgery

Ulcers, neoplasms, filling defects

to pump barium, psyllium,

or sorbitol contrast media directly into small bowel

IBD, malabsorption, weight loss/anemia, Meckel’s diverticulum

Neoplasms, IBD, malabsorption, infection

Right crus of diaphragm

Psoas muscles

Erector spinae muscles

Right kidney

Left kidney Liver

Gallbladder

Spleen Head of he pancreas

Small bowel

Vertebra

a Aorta

b Inferior vena cava

c Superior mesenteric vein

d Superior mesenteric artery

e Left renal artery

a b

c d

me

Abdominal Imaging

Specific Visceral Organ Imaging

Liver

• U/S: assessment of cysts, abscesses, tumours, biliary tree

• CT ± IV: most popular procedure for imaging the liver parenchyma (primary liver tumours, metastases,

cysts, abscesses, trauma, cirrhosis)

• MR: also excellent in evaluation of primary liver tumours, liver metastases, and other parenchymal

conditions, and is particularly helpful in differentiating common benign hepatic hemangiomas from

primary liver tumours and metastases

• elastography: measures shear wave velocity by U/S (Fibroscan) or MRI (MR elastography) to

non-invasively quantify liver fibrosis

• findings

■ advanced cirrhosis: liver small and irregular (fibrous scarring, segmental atrophy, regenerating

nodules)

■ portal HTN: increased portal vein diameter, collateral veins, splenomegaly (≥12 cm), portal vein

thrombosis, recanalization of the umbilical vein

■ porto-systemic shunts: caput medusa, esophageal varices, spontaneous spleno-renal shunt

■ U/S: cirrhosis appears nodular and hyperechoic with irregular areas of atrophy of the right lobe and

hypertrophy of the caudate or left lobes

■ CT: fatty infiltration appears hypodense

• in order to be visualized, some masses require contrast

• upon identifying a liver lesion on imaging (e.g U/S), the follow-up imaging modality should be CT or

MR CT would be four-phase non-contrast, arterial, venous, and delayed to distinguish the common

benign liver lesion hemangioma from other tumours

Table 11 Imaging of Liver Masses

Benign

Hepatic Adenoma Most common in young women taking oral

contraceptives Well-defined mass with hyperechoic areas due to hemorrhage

Well-defined hypervascular lesion with enlarged central vessel becoming slightly isoattenuating in venous phase

scans; central filling and persistent enhancement on delayed scans

Focal Nodular

Hyperplasia Well-defined mass, central scar seen in 50% Hypervascular mass in arterial phase and isoattenuation to liver in portal venous phase

Abscess Ill-defined, irregular margin, hypoechoic contents Low attenuation lesion with an irregular enhancing

wall

calcification

Malignant

HCC Single/multiple masses, or diffuse infiltration Hypervascular; enhances in arterial and washes out

in venous phase with portal venous tumour thrombus

Metastases Multiple masses of variable echotexture Usually low attenuation on contrast-enhanced scan

■ U/S: mass is more echogenic than normal pancreatic tissue

■ CT: preferred modality for diagnosis/staging

• ductal dilation secondary to stone/tumour

■ MRCP: imaging of ductal system using MRI cholangiography; no therapeutic potential

■ ERCP: endoscope to inject dye into the biliary tree and x-ray imaging to assess pancreatic and

biliary ducts; therapeutic potential (stent placement, stone retrieval); acute pancreatitis is a

complication in 5% of diagnostic procedures and 10% of therapeutic procedures

Biliary Tree

• U/S: bile ducts usually visualized only if dilated, secondary to obstruction (e.g choledocholithiasis,

benign stricture mass)

• CT: dilated intrahepatic ductules seen as branching, tubular structures following pathway of portal

venous system

• MRCP, ERCP, PTC: further evaluation of obstruction and possible intervention

Revised Estimates of Diagnostic Test Sensitivity and Specificity in Suspected Biliary Tract Disease

Arch Intern Med 1998;154:2573-2581

Purpose: To assess the sensitivity and specificity

of tests used to diagnose cholelithiasis and acute cholecystitis, including ultrasonography (U/S), oral cholecystography, radionucleotide scanning with Technetium, magnetic resonance imaging (MRI) or computed tomography (CT).

Methods: Meta-analysis of studies evaluating the

use of different imaging modalities in the diagnosis

of biliary tract disease Main outcomes were sensitivity and specificity of the different imaging modalities, using the gold standard of surgery, autopsy, or 3 mo clinical follow-up for cholelithiasis For acute cholecystitis, pathologic findings, confirmation of an alternate disease, or clinical resolution during hospitalization for cholecystitis were used as the standard.

Results: Thirty studies were included For

evaluating cholelithiasis U/S had the best unadjusted sensitivity (0.97; 95% CI 0.95-0.99) and specificity (0.95, 0 88-1.00) and adjusted (for verification bias) sensitivity (0.84; 0.76-0.92) and specificity (0.99; 95% CI 0.97-1.00) For evaluating acute cholecystitis, radionucleotide scanning has the best sensitivity (0.97; 0.96-0.98) and specificity (0.90; 0.86-0.95).

Conclusion: U/S is the test of choice for diagnosing

cholelithiasis and radionucleotide scanning is the superior test for diagnosing acute cholecystitis.

Figure 18 ERCP: biliary tree

Normal liver appears denser than spleen on

CT If less dense, suspect fatty infiltration

Liver Mass DDx

5 Hs HCC Hydatid cyst Hemangioma Hepatic adenoma Hyperplasia (focal nodular)

oo

fre

me oo

fre

c

me o

m b

om

Abdominal maging

“itis” Imaging

Acute Cholecystitis

• pathogenesis: inflammation of gallbladder resulting from sustained gallstone impaction in

cystic duct or, in the case of acalculous cholechystitis, due to gallbladder ischemia or

cholestasis (see General Surgery, GS47)

• best imaging modality: U/S (best sensitivity and specificity); nuclear medicine (HIDA scan) can help

diagnose cases of acalculous or chronic cholecystitis

• findings: Most sensitive findings are presence of gallstones and positive sonographic Murphy’s sign

(tenderness from pressure of US probe over visualized gallbladder) Secondary findings include

thickened gallbladder wall (>3 mm), dilated gallbladder and pericholecystic fluid

• management: admit, NPO, IVF analgesia, cefazolin, early laparoscopic cholecystectomy

Acute Appendicitis

• pathogenesis: luminal obstruction → bacterial overgrowth → inflammation/swelling → increased

pressure → localized ischemia → gangrene/perforation → localized abscess or peritonitis (see General

Surgery, GS27)

• best imaging modality: U/S or CT

• findings

■ U/S: thick-walled appendix, appendicolith, dilated fluid-filled appendix, non-compressible; may also

demonstrate other causes of RLQ pain (e.g ovarian abscess, IBD, ectopic pregnancy)

■ CT: enlargement of appendix (>6 mm in outer diameter), enhancement of appendiceal wall,

adjacent inflammatory stranding, appendicolith; also facilitates percutaneous abscess drainage

management: admit, NPO, IVF, analgesia, cefazolin + metronidazole, appendectomy

Acute Diverticulitis

• pathogenesis: erosion of the intestinal wall (most commonly rectosigmoid) by increased intraluminal

pressure or inspissated food particles → inflammation and focal necrosis → micro- or macroscopic

perforation (see General Surgery, GS31)

• best imaging modality: CT although U/S is sometimes used

• contrast: oral and rectal contrast given before CT to opacify bowel

• findings

■ cardinal signs: thickened wall, mesenteric infiltration, gas-filled diverticula, abscess

■ CT can be used for percutaneous abscess drainage before or in lieu of surgical intervention

■ sometimes difficult to distinguish from perforated cancer (therefore send abscess fluid for cytology

and follow-up with colonoscopy)

■ if chronic, may see fistula (most common to bladder) or sinus tract (linear or branching structures)

• management: ranges from antibiotic treatment to surgical intervention; can use imaging to follow

progression

Acute Pancreatitis

• pathogenesis: activation of proteolytic enzymes within pancreatic cells leading to local

and systemic inflammatory response (see Gastroenterology, G44); a clinical/biochemical diagnosis

• best imaging modality: imaging used to support diagnosis and evaluate for complications (diagnosis

cannot be excluded by imaging alone)

■ U/S good for screening and follow-up

■ CT is useful in advanced stages and in assessing for complications (1st line imaging test)

• findings

■ U/S: hypoechoic enlarged pancreas (if ileus present, gas obscures pancreas)

■ CT: enlarged pancreas, edema, stranding changes in surrounding fat with indistinct fat planes,

mesenteric and Gerota’s fascia thickening, pseudocyst in lesser sac, abscess (gas or thick-walled fluid

collection), pancreatic necrosis (low attenuation gas-containing non-enhancing pancreatic tissue),

hemorrhage

• management: supportive therapy

■ CT-guided needle aspiration and/or drainage done for abscess when clinically indicated

■ pseudocyst may be followed by CT and drained if symptomatic

Chronic Pancreatitis

• pathogenesis: (see Gastroenterology, G45)

• best imaging modality: MRCP (can show calcification and duct obstruction)

• findings: U/S, CT scan, and MRI may show calcifications, ductal dilatation, enlargement of the pancreas

and fluid collections (e.g pseudocysts) adjacent to the gland

Computed Tomography and Ultrasonography

to Detect Acute Appendicitis in Adults and Adolescents

Ann Intern Med 2004;141:537-546

Purpose: To review the diagnostic accuracy of

computed tomography (CT) and ultrasonography (U/S) in the diagnosis of acute appendicitis.

Methods: Meta-analysis of prospective studies

evaluating the use of CT or U/S, followed by surgical

or clinical follow-up in patients with suspected appendicitis Patients aged ≥14 years with a clinical suspicion of appendicitis were eligible Sensitivity and specificity using surgery or clinical follow-up as the gold standard were the main outcomes studied.

Results: Twenty-two tudi s were included CT (12

studies) had an overall sensitivity of 0.94 (95% CI 0.91-0.95) and a specificity of 0.95 (0.93-0.96) U/S (14 studies) had an overall sensitivity of 0.86 (0.83- 0.88) and a specificity of 0.81 (0.78-0.84).

Conclusion: CT is more accurate for diagnosing

appendicitis in adults and adolescents, although verification bias and inappropriate blinding of reference standards were noted in the included studies.

Figure 19 Ultrasound: inflamed gallbladder

Figure 20 Ultrasound: inflamed appendix

book

fre

me oo

Genitourinary System and Adrenal

Angiography of Gastrointestinal Tract

• anatomy of the GI tract arterial blood supply branches

■ celiac artery: hepatic, splenic, gastroduodenal, left/right gastric

■ superior mesenteric artery: jejunal, ileal, ileo-colic, right colic, middle colic

■ inferior mesenteric artery: left colic, superior rectal

• imaging modalities

■ conventional angiogram: invasive (usual approach via femoral puncture), catheter used

◆ flush aortography: catheter injection into abdominal aorta, followed by selective arteriography of

individual vessels

■ CT angiogram: modality of choice, non-invasive using IV contrast (no catheterization required)

Genitourinary System and Adrenal

Urological Imaging

KUB (Kidney, Ureter, and Bladder X-ray)

• a frontal supine radiograph of the abdomen

• indication: useful in evaluation of radio-opaque renal stones (all stones but uric acid and indinavir)

indwelling ureteric stents/catheters, and foreign bodies in abdomen

• findings: addition of IV contrast excreted by the kidney (intravenous urogram) allows greater

visualization of the urinary tract, but has been largely replaced by CT urography

Abdominal CT

Renal Masses

• Bosniak classification for cystic renal masses

• class I-II: benign and can be disregarded

• class IIF: should be followed

• class III-IV: suspicious for malignancy, requiring additional workup

Table 12 Bozniak Classification for Cystic Renal Masses

Simple Renal Cysts

Class I Fluid-attenuating well-defined lesion no septation, no calcification, no solid components, hair thin wall

Class II Same as class I + fine calcification or moderately thickened calcification in septae or walls also includes

hyperdense cysts (<3 cm) that do not enhance with contrast

Complex Renal Cysts

Class III Thick irregular walls ± calcifications ± septated, enhancing walls or septa with contrast

Renal Cell Carcinoma

Class IV Same as class III + soft tissue enhancement with contrast (defined as >10 Hounsfield unit increase,

characterizing vascularity) with de-enhancement in venous phase ± areas of necrosis

• plain CT KUB indications: general imaging of renal anatomy, renal colic symptoms, assessment of renal

calculi (size and location), and hydronephrosis prior to urological treatment

• CT urography indications: investigation of cause of microscopic/gross hematuria, detailed assessment

of urinary tracts (excretory phase), high sensitivity (95%) for uroepithelial malignancies of the upper

urinary tracts, assessment of renal calculi

■ phases: unenhanced, excretory

• renal triphasic CT indications: standard imaging for renal masses, allows accurate assessment of renal

arteries and veins, better characterization of suspicious renal masses, especially in differentiating renal

cell carcinoma from more benign masses, and pre-operative staging

■ phases: unenhanced, arterial and venous (nephrographic), excretory

Ultrasound

• indications: initial study for evaluation of kidney size and nature of renal masses (solid vs cystic renal

masses vs complicated cysts); technique of choice for screening patients with suspected hydronephrosis

(no IV contrast injection, no radiation to patient, and can be used in patients with renal failure); TRUS

useful to evaluate prostate gland and guide biopsies; Doppler U/S to assess renal vasculature

• findings: solid renal masses are echogenic (bright on U/S), cystic renal masses have smooth

well-defined walls with anechoic interior (dark on U/S), and complicated cysts have internal echoes within a

thickened, irregular wall

Figure 21 Triphasic CT of an angiomyolipoma: showing fat density with

non-contrast scan, mildly enhancing with contrast

NON CONTRAST

VENOUS ARTERIAL

Angiography requires active blood loss

1-1.5 mL/min under optimal conditions for a bleeding site to be visualized in cases of lower

GI bleeding

Imaging Modality Based on Presentation

• Acute testicular pain = Doppler, U/S

• Amenorrhea = U/S, MRI (brain)

• Bloating = U/S, CT

• Flank pain = U/S, CT

• Hematuria = U/S, Cystoscopy, CT

• Infertility = HSG, MRI

• Lower abdominal mass = U/S, CT

• Lower abdominal pain = U/S, CT

• Renal colic = U/S, KUB, CT

• Testicular mass = U/S

• Urethral stricture = Urethrogram

ok

fre

m boo

Genitourinary System and Adrenal

Retrograde Pyelography

• indications: visualize the urinary collecting system via a cystoscope, ureteral catheterization, and

retrograde injection of contrast medium, visualized by radiograph or fluoroscopy; ordered when the

intrarena collecting system and ureters cannot be opacified using intravenous techniques (patient with

impaired renal function, high grade obstruction)

• findings: only yields information about the collecting systems (renal pelvis and associated structures),

no information regarding the parenchyma of the kidney

Voiding Cystourethrogram

• bladder filled with contrast to the point where voiding is triggered

• fluoroscopy (continuous, real-time) to visualize bladder

• indications: children with recurrent UTIs, hydronephrosis, hydroureter, suspected lower urinary tract

obstruction or vesicoureteral reflux

• findings: contractility and evidence of vesicoureteric reflux

Retrograde Urethrogram

• a small Foley catheter placed into penile urethral opening

• indications: used mainly to study strictures or trauma to the male urethra; first-line study if trauma with

blood present at urethral meatus

MRI

• advantages: high spatial and tissue resolution, lack of exposure to ionizing radiation and nephrotoxic

contrast agents

• indications: indicated over CT for depiction of renal masses in patients with previous nephron sparing

surgery, patients requiring serial follow-up (less radiation dosage), patients with reduced renal function,

patients with solitary kidneys, clinical staging of prostate cancer (endorectal coil MRI)

Renal Nuclear Scan

Table 13 Renal Scan Tests

Renogram Assess renal function and collecting system: evaluation

of renal failure, workup of urinary tract obstruction and

renovascular HTN, investigation of renal transplant

IV 99m Tc-pentetate (DTPA) or mertiatide (MAG3), and imaged at 1-3 s intervals with a gamma camera over the first 60 s to assess perfusion

Morphological Assess renal anatomy: investigation of pyelonephritis

and cortical scars

99m Tc-DMSA 99m Tc-glucoheptonate

Gynecological Imaging

Ultrasound

• transabdominal and transvaginal are the primary modalities, and are indicated for different scenarios

• transabdominal requires a full bladder to push out air-containing loops of bowel

■ indications: good initial investigation for suspected pelvic pathology

• TVUS provides enhanced detail of deeper/smaller structures by allowing use of higher frequency sound

waves at reduced distances

■ indications: improved assessment of ovaries, first trimester development, and ectopic pregnancies

Hysterosalpingogram

• performed by x-ray images of the pelvis after cannulation of the cervix and subsequent injection of

opacifying agent

• indications: useful for assessing pathology of the uterine cavity and fallopian tubes, evaluating uterine

abnormalities (e.g bicornuate uterus), or evaluation of fertility (absence of flow from tubes to peritoneal

cavity indicates obstruction)

CT/MRI

indications: evaluating pelvic structures, especially those adjacent to the adnexa and uterus

• invaluable for staging gynecological malignancies and detecting recurrence

Sonohysterogram

• saline infusion sonohysterogram involves injecting fluid into the uterine cavity transcervically to

provide enhanced endometrial visualization during TVUS examination

• indications: abnormal uterine bleeding, uterine cavity abnormalities that are suspected or noted on

TVUS (e.g leiomyomas polyps, synechiae), congenital abnormalities of the uterine cavity, infertility,

recurrent pregnancy loss

• contraindications: pregnancy, pelvic infection

Pregnancy should always be ruled out by β-hCG before CT of a female pelvis (or any organ system) is performed

Figure 24 Transabdominal U/S:

Figure 22 Triphasic CT of a renal cell carcinoma: showing arterial enhancing right

renal lesion with venous washout (shunting)

VENOUS PHASE

NON CONTRAST CT

ARTERIAL PHASE

ee.com

co

sfr

Table 14 Typical and Atypical Findings on a Sonohysterogram

Polyps A well-defined, homogeneous, polypoid lesion isoechoic

to the endometrium with preservation of the myometrial interface

endometrial-Atypical features include cystic components, multiple polyps, broad base, hypoechogenicity or heterogeneity

Leiomyoma Well-defined, broad-based, hypoechoic, solid masses with

shadowing Overlying layer of endometrium is echogenic and distorts the endometrial-myometrial interface

Pedunculation or multilobulated surface

Hyperplasia and

Cancer Diffuse echogenic endometrial thickening without focal abnormality, although focal lesions can occur Endometrial

cancer is typically a diffuse process, but early cases can

be focal and appear as a polypoid mass

Adhesions Mobile thin, echogenic bands that cut across the

endometrial cavity Thick broad-based bands that can completely obliterate the endometrial

cavity, as in Asherman’s syndrome

Adrenal Mass

• imaging modality: most often identified on CT scan as ‘incidentaloma,’ can also use CT/MRI to

distinguish benign from malignant masses

Table 15 Adrenal Mass Findings on CT and MRI

round/oval Irregular with unclear margins Round/oval with clear margins Oval/irregular with unclear margins

mixed densities Heterogeneous with cystic areas Heterogeneous with mixed densities

Washout of Contrast

(<1 cm/yr) Usually rapid (>2 cm/yr) Slow (0.5-1 cm/yr) Variable

Other Findings Usually low density due

to intracellular fat Necrosis, calcifications, and hemorrhage Hemorrhage Occasionally hemorrhage

MRI on T2 Weighted

Imaging Isointense in relation to liver Hyperintense in relation to liver Markedly hyperintense in relation to liver Hyperintense in relation to liver

Neuroradiology

Modalities

• CT is the modality of choice for most neuropathology; even under circumstances where MRI is

preferred, CT is frequently the initial study performed because of its speed, availability, and lower cost

■ acute head trauma: CT is best for visualizing “bone and blood”; MRI is used only when CT fails to

detect an abnormality despite strong clinical suspicion

■ acute stroke: MRI ideal, CT most frequently used

■ suspected subarachnoid or intracranial hemorrhage

■ meningitis: rule out mass effect (e.g cerebral herniation, shift) prior to lumbar puncture

■ tinnitus and vertigo: CT and MRI are used in combination to detect bony abnormalities and CN

VIII tumours, respectively

Skull Films

• rarely performed, generally not indicated for non-penetrating head trauma

• indications: screening for destructive bony lesions (e.g metastases), metabolic disease, skull anomalies,

post-operative changes and confirmation of hardware placement, skeletal surveys, multiple myeloma

CT

• indications: excellent study for evaluation of bony and intracranial abnormalities

• often done first without and then with IV contrast to show vascular structures or anomalies

• vascular structures and areas of blood-brain barrier impairment are opaque (e.g hyperattenuating or

white/show enhancement) with contrast injection

■ when in doubt, look for Circle of Willis or confluen e of sinuses to determine presence of contrast

enhancement

Figure 26 Epidural hematoma

Figure 27 Subdural hematoma

Figure 28 Subarachnoid hemorrhage

Figure 29 Intraparenchymal hemorrhage

Modality Based on Neuropathology Presentation

• Cognitive decline = CT

• Cord compression = MRI

• Decreased level of consciousness = CT

• Fish bone/other swallowed foreign body = CT

• Low back pain, radiculopathy = MRI

• Multiple sclerosis = MRI

• Neck infection = CT

• Orbital infection = CT

• Rule out bleed = CT

• Rule out aneurysm = CTA, MRA

Neurorad ology

• posterior fossa can be obscured by extensive bony-related streak artifact

• rule out skull fracture, epidural hematoma (lenticular shape), subdural hematoma (crescentic shape),

subarachnoid hemorrhage, space occupying lesion, hydrocephalus, and cerebral edema

• multiplanar imaging can be performed with newer gener tion of multidetector CT scanners

Myelography

• introduction of water-soluble, low-osmotic contrast media into subarachnoid space using lumbar

puncture followed by x-ray or CT scan

• indications: excellent study for disc herniations, traumatic nerve root avulsions, patients with

contraindication to MRI

MRI

• indications: shows brain and spinal soft tissue anatomy in fine detail, clearly distinguishes white

from grey matter (especially T1-weighted series), multiplanar reconstruction helpful in pre-operative

assessment

Cerebral Angiography/CT Angiography/MR Angiography

• indications: evaluation of vascular lesions such as atherosclerotic disease, aneurysms, vascular

malformations, arterial dissection

• conventional digital subtraction angiography remains the gold standard for the assessment of neck and

intracranial vessels; however, it is an invasive procedure requiring arterial (femoral) puncture; catheter

manipulation has risk of vessel injury (e.g dissection, occlusion, vasospasm, emboli)

• MRA methods (phase contrast, time of flight, gadolinium-enhanced) and CTA are much less invasive

without actual risk to intracranial or neck vessels

• MRA and CTA are often used first as ‘screening tests’ for the assessment of subarachnoid hemorrhage,

vasospasm, aneurysms

Figure 30 Hydrocephalus: ventricular dilatation (may see periventricular low attenuation due to transependymal CSF flow)

Table 16 Two Types of Hydrocephalus

Communicating/Extra-Ventricular Obstruction distal to the ventricles (e.g at the level of the arachnoid granulations); imaging

shows all ventricles dilated

Non-Communicating Obstruction within the ventricular system (e.g mass obstructing the aqueduct or foramen of

Monro); imaging shows dilatation of ventricles proximal to the obstruction

Nuclear Medicine

• SPECT using 99mTc-exametazime (HMPAO) and 99mTc-bicisate (ECD) imaging assesses cerebral

blood flow by diffusing rapidly across the blood brain barrier and becoming trapped within neurons

proportional to cerebral blood flow

• 18FDG PET imaging assesses cerebral metabolic activity

• indications: differentiation of residual tumour vs radiation necrosis; localizing of epileptic seizure foci;

evaluation of atypical dementia

Approach to CT Head

• think anatomically, work from superficial to deep

• scan: confirm that the imaging is of the correct patient, whether contrast was used, if the patient is

aligned properly, if there is artifact present

• skin/soft tissue: examine the soft tissue superficial to the skull, looking for thickening suggestive of

hematoma or edema; also evaluate the ear, orbital contents (globe, fat, muscles), parotid gland, muscles

of mastication (masseter, temporalis, pterygoids), visualize pharynx

• bone and airspace (use the bone window): check calvarium, visualize mandible, visualize C-spine

(usually C1 and maybe part of C2) for fractures, absent bone, lytic/sclerotic lesions; inspect sinuses and

mastoid air cells for opacity that may suggest fluid, pus, blood, tumour, or fracture; status of the orbital

floor in cases of facial trauma (coronal series best)

Figure 31 Vertebrobasilar circulation

(note the incidental basilar tip aneurysm)

Transient ischemic attacks are not associated with radiological findings

Approach to the CT Head Some = Scan Sore = Skin/Soft Tissue Brains = Bone/Airspace Demonstrate = Dura/Subdural space Pushed = Parenchyma Ventricles = Ventricles/Sulci/Cisterns

bo

ksfre

m b ksfre

c

m b

booksfre

m

bo ks

e.c m

b

ee co

• dura and subdural space: crescent-shaped hyperdensity in the subdural space suggests subdural

hematoma; lentiform hyperdensity in the epidural space suggests epidural hematoma; check symmetry

of dural thickness, where increased thickness may suggest the presence of blood

• parenchyma: asymmetry of the parenchyma suggests midline shift; poor contrast between grey and

white matter suggests possible infarction, tumour, edema, infection, or contusion; hyperdensity in the

parenchyma suggests enchancing lesions, intracerebral hemorrhage, or calcification; central grey matter

nuclei (e.g globus pallidus, putamen, internal capsule) should be visible, otherwise, suspect infarct,

tumour, or infection

• ventricles/sulci/cisterns: examine position of ventricles for evidence of midline compression/shift;

hyperdensities in the ventricles suggest ventricular/subdural hemorrhage; enlarged ventricles suggest

hydrocephalus; obliteration of sulci may suggest presence of edema causing effacement, possible blood

filling in the sulci, or tumour; cistern hyperdensities may suggest blood, pus, or tumour

• please refer to Toronto Notes website for supplementary material on how to approach a head CT

Selected Pathology

• see Neurosurgery, NS20 for intracranial mass lesions

• see Neurosurgery, NS29 and Plastic Surgery, PL29 for head trauma

• see Emergency Medicine, ER7 for vertebral trauma

• see Neurosurgery, NS27 and Orthopedics, OR22 for degenerative spinal abnormalities

Cerebrovascular Disease (see Neurology, N6 and Neurosurgery, NS17)

• pathogenesis of stroke: see Neurology, N48

• best imaging modality: infarcts best detected by MRI > CT

Table 17 Temporal Findings of Infarction with CT and MRI

Hyperacute (0 24 h) Usually normal within 6 h

Edema (loss of grey-white matter differentiation –

“insular ribbon sign”, effacement of sulci, mass ef ect) Hyperattenuating artery “hyperdense MCA sign” repre- senting intravascular thrombus/emboli may be seen in ischemic stroke

Hyperattenuating acute blood surrounded by edema may be seen in hemorrhagic stroke

Hyperintensity on DWI within minutes of arterial occlusion due to restriction of water movement indicative of cytotoxic edema Hypointensity on ADC within minutes Hyperintensity upon T2/FLAIR approximately

6 h after onset due to edema (loss of white matter differentiation, effacement of sulci, mass effect)

grey-Acute (24 h-1 wk) Increasing edema (seen as hypoattenuation) may

result in significant positive mass effect Continued hyperintensity on DWI Hypointensity on ADC reaches nadir at 3-5 d

and begins to increase Continued hyperintensity on T2/FLAIR

Subacute (1-3 wk) Resolution of edema leads to increased attenuation of

infarcted area that may regain near-normal density and mask stroke “fogging phenomenon”

Continued hyperintensity on DWI due to “T2 shine through”

Intensity on ADC continues to rise, pseudonormal-izes at 10-15 d, and then surpasses that of sur-rounding normal tissue Continued hyperintensity on T2/FLAIR

Chronic (>3 wk) Encephalomalacia (parenchymal volume loss) appears

as hypoattenuation with negative mass effect Hyperintensity on DWI/T2/FLAIR progressively decreases

ADC intensity remains elevated

• carotid artery disease

■ best imaging modality: Duplex Doppler U/S

■ other modalities: MRA or CTA if carotid angioplasty or endarterectomy is under consideration

(conventional angiography reserved for inadequate MRA or CTA)

Multiple Sclerosis (see Neurology, N52)

• best imaging modality: MRI has high sensitivity in diagnosing MS (>90%) but low specificity (71-74%)

• findings

■ characteristic lesion on MRI is cerebral or spinal plaque

■ plaques typically found in periventricular region, corpus callosum (arranged at right angles to the

corpus callosum) centrum semiovale, and to a lesser extent in deep white matter structures and

basal ganglia

■ “Dawson’s fingers” refers to perivenular regions of demyelination that are seen to radiate outwards

into the deep periventricular region

■ plaques usually have ovoid appearance, hyperintense on T2 and hypointense on T1

■ conventional T2 may underestimate plaque size and overall plaque burden – advanced techniques

(diffusion tensor imaging and MR spectroscopy can be of use

Figure 33 CT images of early infarct: (A) absence of left insular ribbon (B) hyperdense artery

stroke to rule out hemorrhageNon-contrast CT Hemorrhage absent diffusion-weighted sequence or a CTA To detect infarct, MR scan with

Figure 32 Insular Ribbon Sign (Left side)

Hypodensity of insular cortex representing early sign of infarction

Ddx for Ring Enhancing Cerebral Lesion MAGIC DR

Metastasis Abscess Glioblastoma multiforme Infarction (subacute/chronic) Contusion/hematoma Demyelinating disease (e.g MS) Radiation necrosis

ooksfre

m booksfre

c

m boo

Musculoskeletal System

■ perivascular and interstitial edema may be prominent

■ spinal cord lesions typical of MS

◆ little or no cord swelling

◆ unequivocal hyperintensity on T2-weighted sequences

size at least 3 mm but less than 2 vertebral segments in length

◆ occupy only part of the cord in cross-section

◆ focal (i.e clearly delineated and circumscribed on T2-weighted sequences)

CNS Infections

• leptomeningitis

■ pathogenesis: inflammation of the pia or arachnoid mater, most often secondary to hematogenous

spread from infection or via organisms gaining access across areas not protected by the blood-brain

barrier (choroid plexus or circumventricular organs)

◆ pathogens include: S p neumoniae, H influenzae, N meningitidis, L monocytogenes

■ best imaging modality: MRI (T2-weighted/FLAIR) superior to CT

■ findings

◆ meningeal enhancement (following the gyri/sulci and/or basal cisterns), hydrocephalus

(communicating), cerebral swelling, subdural effusion

◆ a normal MRI does not rule out leptomeningitis

• herpes simplex encephalitis (see Infectious Diseases, ID19)

■ pathogenesis: inflammation of the brain parenchyma secondary to infection with herpes simplex

virus, asymmetrically affects the limbic regions of the brain (i.e temporal lobes, orbitofrontal region,

insula, and cingulate gyrus)

■ best imaging modality: MRI (T1- and T2 weighted)

■ findings

◆ acute (within 4-5 d): asymmetric high intensity lesions on T2 MRI in temporal and inferior

frontal lobes strongly suggestive

◆ DDx: infarct, tumour, status epilepticus, limbic encephalitis

◆ CT may show low density in temporal lobe and insula; rarely basal ganglia involvement

◆ long-term may show parenchymal loss to affected areas

• cerebritis/cerebral abscess

◆ pathogenesis: an infection of the brain parenchyma (cerebritis) which can progress to a

collection of pus (abscess), most frequently due to hematogenous spread of infectious organisms,

commonly located in the distribution of the MCA

◆ pathogens include: S aureus (often in IV drug users, nosocomial), Streptococcus, Gram negative

bacteria, Bacteroides

■ best imaging modality: MRI including DWI imaging series (abscess will be DWI positive); CT still

used as a viable alternative

■ findings according to one of four stages of abscess formation

◆ early cerebritis (1-3 d): inflammatory infiltrate with necrotic centre, low intensity on T1, high

intensity on T2

◆ late cerebritis (4-9 d): ring enhancement may be present

◆ early capsule (10-13 d): ring enhancement

◆ late capsule (14 d or greater): well demarcated ring-enhancing lesion, low intensity core, with

mass effect; considerable edema around the lesion, seen as hyperintensity on T2

Musculoskeletal System

Modalities

• see Imaging Modalities, MI2 for advantages and disadvantages of the following

Plain Film/X-Ray

• usually initial study used in evaluation of bone and joint disorders

• indications: fractures and dislocations, arthritis, assessment of malalignment, orthopedic hardware, and

bone tumours (initial)

• minimum of two films orthogonal to each other (usually AP and lateral) to rule out a fracture

• image proximal and distal joints, particularly important with paired bones (e.g radius/ulna)

• minimally effective in evaluating soft tissue injury

CT

• evaluation of fine bony detail

• indications: assessment of complex, comminuted, intra-articular, or occult fractures including distal

radius, scaphoid, skull, spine, acetabulum, calcaneus, and sacrum

• evaluation of soft tissue calcification/ossification

MRI

• indications: evaluation of internal derangement of joints (e g ligaments, joint capsule, menisci, labrum,

cartilage), assessment of tendons and muscle injuries, characterization and staging of soft tissue and

bony masses

Figure 35 T2-weighted FLAIR: (A) sagittal (B) axial images of multiple sclerosis with periventricular “Dawson’s Fingers”

A

B

Figure 36 T2-weighted (FLAIR) coronal image of herpes simplex virus encephalitis affecting temporal lobes

oksfree.c

m

m b

Musculoske etal System

Ultrasound

• indications: tendon injury (e.g rotator cuff, Achilles tendon), detection of soft tissue masses and to

determine whether cystic or solid, detection of foreign bodies, U/S-guided biopsy and injections

• Dopple determines vascularity of structures

Nuclear Medicine (Bone Scintigraphy)

• determine the location and extent of bony lesions

99mTc-methylene diphosphonate localizes to areas of increased bone turnover or calcification – growth

plate in children, tumours, infections, fractures, metabolic bone disease (e.g Paget’s), sites of reactive

bone formation, and periostitis

• advantages: very sensitive, capable of imaging entire body with relatively low dose radiation

• disadvantages: low specificity, not widely available due to special requirements (e.g gamma camera,

radiopharmaceuticals)

Approach to Bone X-Rays

• identification: name, MRN, age of patient, type of study, region of investigation

• soft tissues: swelling, calcification/ossification

• joints: alignment, joint space, presence of effusion, osteophytes, erosions, bone density, overall pattern,

and symmetry of affected joint

• bone: periosteum, cortex, medulla, trabeculae, density articular surfaces, bone destruction, bone

production, appearance of the edges or borders of any lesions

Trauma

Fracture/Dislocation

• description of fractures

• site of fracture (bone, region of bone, intra-articular vs extra-articular)

• pattern of fracture line (simple vs comminuted)

• displacement (distal fragment with reference to the proximal fragment)

• soft tissue involvement (calcification, gas, foreign bodies)

• type of fracture (stress vs pathologic)

• for specific fracture descriptions and characteristics of fractures, see Orthopedics, OR4

Arthritis

• joint space narrowing – typically non-uniform • joint space narrowing – typically uniform

Bone Tumour

Approach

• metastatic tumours to bone are much more common than primary bone tumours, particularly if age

>40 yr

■ diagnosis usually requires a biopsy if primary not located

■ few benign tumours/lesions have potential for malignan transformation

■ MRI is good for tissue delineation and pre-operative assessment of surrounding soft tissues,

neurovascular structures, and medullary/marrow involvement

■ plain film is less sensitive than other modalities but useful for assessing aggressiveness and

constructing differential diagnosis

Considerations and Tumour Characteristics

• for specific bone tumours, see Orthopedics, OR45

• age: most common tumours by age group

■ <1 yr of age: metastatic neuroblastoma

■ 1-20 yr of age: Ewing’s sarcoma in tubular bones

■ 10-30 yr of age: osteosarcoma and Ewing’s tumour in flat bones

■ >40 yr of age: metastases, multiple myeloma, and chondrosarcoma

• multiplicity: metastases, myeloma, lymphoma, fibrous dysplasia, enchondromatosis

• location within bone

■ epiphysis: giant cell tumour, chondroblastoma, geode, eosinophilic granuloma, infection

■ metaphysis: simple bone cyst, aneurysmal bone cyst, enchondroma, chondromyxoid fibroma,

nonossifying fibroma, osteosarcoma, chondrosarcoma

■ diaphysis: fibrous dysplasia, aneurysmal bone cyst, brown tumours, eosinophilic granuloma, Ewing’s

e

oksf

ee.com

Musculoskeletal System

• expansile

■ aneurysmal bone cyst, giant cell tumour, enchondromas, brown tumours, metastases (especially

renal and thyroid), plasmacytoma

• matrix mineralization

■ chondroid (popcorn calcification) or osseous

• margin/zone of transition: area between lesion and normal bone

• cortex: intact, disturbed

• periosteal reaction: onion-skinning, sunburst, Codman’s triangle, periosteal neocortex

• soft tissue mass

Figure 39 Radiographic appearance of bone remodelling and destruction processes

Table 18 Characteristics of Benign and Malignant Bone Lesions

Thin sclerotic margin/sharp delineation of lesion

Overlying cortex intact

No or simple periosteal reaction

No soft tissue mass

Poor delineation of lesion – wide zone of transition Loss of overlying cortex/bony destruction Periosteal reaction

Soft tissue mass

Metastatic Bone Tumours

• all malignancies have potential to metastasize to bone

• metastases are 20-30x more common than primary bone tumours

• metastasis can cause a lytic or a sclerotic reaction when seeding to bone

• when a primary malignancy is first detected, a bone scan is often part of the initial workup

• may present with pathological fractures or pain

• biopsy or determination of primary is the only way to confirm the diagnosis

• most common metastatic bone tumours: breast, prostate, lung, see Orthopedics, OR45

Table 19 Characteristic Bone Metastases of Common Cancers

Thyroid

Melanoma (KLM: flies to the periphery)

• 99mTc, followed by 111In-labeled white cell scan or gallium radioisotope scan

• plain film changes visible 8-10 d after process has begun

■ soft tissue swelling

■ local periosteal reaction

■ pockets of air (from anaerobes) may be seen in the tissues, may also suggest necrotizing fasciitis

■ mottled and nonhomogeneous with a classic “moth-eaten” appearance

■ cortical destruction

Margination

of lesions Patterns of cortical disturbance Patterns of medullary destruction Periosteal new bone formation

Punched out

Thin rim of sclerosis

Thick rim of sclerosis

Expansile Endosteal scalloping Invisible margin Saucerizat on

Permeative

Moth-eaten

Onion-skin layered Codman's Triangle Hair-on-end spiculated Sunburst divergent Solid undulating © Patrick Cervini 2002

• Aneurysmal bone cyst

• Langerhans cell histiocytosis

• Myositis ossificans

Periosteal Reaction

• “Onion skinning” = Ewing’s sarcoma

• “Sunburst”, “hair on end” = osteosarcoma

• “Codm n’s triangle” = osteosarcoma,

Ew ng s sarcoma, subperiosteal abscess

Lytic = decreased density Sclerotic = increased density

ee.co

booksf

ee c

Musculoske etal System

Bone Abscess

• overlying cortex has periosteal new bone formation

• sharply outlined radiolucent area with variable thickness in zone of transition

• variable thickness periosteal sclerosis

• sequestrum: a piece of dead bone within a Brodie’s abscess

• a sinus tract or cloaca may communicate between the abscess through the cortex to the surface of the

• DEXA: gold standard for measuring bone mineral density

■ T-score: the number of standard deviations from the young adult mean, most clinically valuable

◆ osteopenia: –2.5 < T-score < –1

◆ osteoporosis: T-score ≤–2.5

■ Z-score: the number of standard deviations from the age-matched mean

■ risk of fracture: related to bone mineral density, age, history of previous fractures, steroid therapy

■ diagnostic sensitivity of DEXA highest when bone mineral density measured at lumbar spine and

proximal femur

• appearance on plain film

■ osteopenia: reduced bone density on plain films

◆ may also be seen with osteomalacia, hyperparathyroidism, and disuse

■ compression of vertebral bodies

■ biconcave vertebral bodies (“codfish” vertebrae)

■ long bones have appearance of thinned cortex and increased medullary cavity

◆ look for complications of osteoporosis (e.g insufficiency fractures: hip, vertebrae, sacrum, pubic

• usually due to vitamin D deficiency, resulting in softening and bowing of long bones

• similar to osteoporosis, initial radiological appearance of osteopenia (coarse and poorly defined bone

texture)

“fuzzy”, ill-defined trabeculae

• Looser’s zones (pseudofracture)

■ characteristic radiologic feature

■ fissures or clefts at right angles to long bones and extending through cortex

■ DDx: chronic renal disease, fibrous dysplasia, hyperthyroidism, Paget’s, osteodystrophy, X-linked

hypophosphatemia

Figure 40 Osteomalacia, osteopenia, and osteoporosis

ll defined, poorly mineralized trebeculae

Coarse texture

Decreased bone mass, but above threshold for osteoporosis

Looser’s fracture Bowing of ong bone

Increased pore size, decreased bone mass

Continuing vertebral compression Biconcave vertebral bodies

© Krista Shapton 2010

Osteoporosis

Reduced amount of bone

OsteoMalacia

Normal amount of bone, but reduced

Mineralization of normal osteoid

oo

sfree

co

m boo

re co

• resorption of bone typically in hands (subperiosteal and at tufts), sacroiliac joints (subchondral), skull

(“salt and pepper” appearance), osteoclastoma (brown tumours)

• “rugger jersey spine”: band-like osteosclerosis at superior/inferior margins of vertebral bodies

Paget’s Disease

• abnormal remodelling involving single or multiple bones – especially skull, spine, pelvis

• 3 phases: 1st phase = lytic, 2nd phase = mixed (lytic/sclerotic), 3rd phase = sclerotic

• 99mTc-exametazime (HMPAO) and 99mTc-bicisate (ECD) imaging used in SPECT to assess cerebral blood

flow and cellular metabolism, taken up predominantly in grey matter

■ used for dementia, traumatic brain injury, and to a lesser extent vasculitis, neuropsychiatric

disorders, and occasionally stroke

■ most commonly used tracers to confirm brain death (i.e absent blood flow to the brain and absent

uptake on delayed planar and SPECT images in brain and brainstem, assuming study is technically

adequate)

■ either tracer can be used for seizure imaging to assess for the most likely location of epileptogenic

focus but usually must be made available for 24 h and the patient followed by a nurse who is

competent to administer the activity at the time of seizure

• PET imaging assesses metabolic activity most commonly with 18FDG; used for dementia imaging, grade

and stage of brain tumours, occasionally for seizure disorder imaging, and vasculitis; PET imaging with

amyloid tracers for diagnosis of Alzheimer’s disease is becoming more common

• CSF imaging, intrathecal administration of 111In DTPA to evaluate CSF leak or to differentiate normal

pressure hydrocephalus from brain atrophy

• CSF shunt evaluation for obstruction (most commonly ventriculoperitoneal) with sterile or pyrogen

free 99mTc (usually) or 111In-DTPA; small quantity of activity is injected into the reservoir under sterile

conditions and should flow freely into the peritoneal cavity by 45 min; maneuvers such as pumping the

shunt, sitting the patient upright or ambulating are acceptable to encourage flow during this time

• adrenergic imaging of the heart with MIBG has been used to differentiate dementias with autonomic

dysfunction (i.e Lewy Body and Parkinson’s disease) from other forms of dementia (i.e autonomic

impairment associated with decreased MIBG activity in the heart)

Thyroid

Radioactive Iodine Uptake (see Endocrinology, E21)

• index of thyroid function (trapping and organification of iodine)

• radioactive 131I given PO to fasting patient (small quantity)

• measure percentage of administered iodine taken up by thyroid

• increased RAIU: toxic multinodular goitre, toxic adenoma, Graves’ disease

• decreased RAIU: subacute thyroiditis, late Hashimoto’s disease, exogenous thyroid hormone or iodine,

falsely decreased in patient with recent radiographic contrast studies, high dietary iodine (e g seaweed,

taking a “thyroid vitamin”)

• important – iodine uptake helps in the differential of hyperthyroidism only, not hypothyroidism

(exception is pediatrics)

Thyroid Imaging (Scintiscan)

• 99mTc-pertechnetate IV or radioactive iodine (123I); most Canadian sites use pertechnetate to reduce cost

• provides functional anatomic detail

• hot (hyperfunctioning) lesions: usually benign (e.g adenoma, toxic multinodular goitre), cancer very

unlikely (less than 1%)

• cold (hypofunctioning) lesions: cancer must be considered until biopsy negative even though only

6-10% are cancerous; decision to biopsy should be based on clinical and sonographic features

• isointense i.e “warm” lesions: cancer must be considered as an isointense lesion may represent cold

nodules superimposed on normal tissue; if cyst suspected, correlate with U/S

Figure 41 Multinodular goitre (top) Cold nodule (bottom)

c

m o

ee.co

me o

Nuclear Medicine

Radioiodine Ablation

• 131I for Graves’ disease, multinodular goitre, thyroid cancer (in the case of thyroid cancer, ablation

performed at higher dose and after thyroidectomy)

• serum thyroglobulin used to detect recurrent thyroid cancer in a patient that has received ablation

• advice should be given for patient-specific precautions to remain away from family members and

caregivers to reduce radiation exposure after thyroid ablation, do not initiate pregnancy for 6 mo, small

risk of exophthalmos, thyroid storm, secondary malignancy

Pediatric Hypothyroidism

• pertechnetate thyroid scan can differentiate thyroid agenesis, hemiagenesis, lingular thyroid,

organification defect, however should not wait for a diagnosis to start thyroid hormone replacement in

a neonate; start immediately

Respiratory

V/Q Scan

examine areas of lung in which ventilation and perfusion do not match

• ventilation scan

■ patient breathes radioactive gas (nebulized 99mTc-DTPA, 133Xe, or most commonly Technegas)

through a closed system, filling alveoli proportionally to ventilation

■ ventilation scan defects indicate: airway obstruction (i.e air trapping), chronic lung disease,

bronchospasm, tumour mass obstruction

• perfusion scan

■ radiotracer injected IV (99mTc-MAA) → trapped in pulmonary capillaries (0.1% of arterioles

occluded) according to blood flow

■ relatively contraindicated in severe pulmonary HTN, right-to-left shunt, previous history of

pneumonectomy, small child In these cases fewer particles are usually given

• to rule out PE

■ indications: some institutions favour in pregnancy (lower radiation dose to breast than CT), or

where CT contrast contraindicated (e.g contrast allergy, renal failure)

■ areas of lung that are well-ventilated but not perfused (unmatched defect) are suspicious for acute

infarction

■ defects are wedge-shaped, extend to periphery, usually bilateral and multiple

■ often reported as high probability (> 2 large i.e segmental mismatched perfusion defects),

intermediate, low, very low, or normal according to modified PIOPED II criteria although now are

increasingly reported as PE present, indeterminate or normal

■ useful in finding clinically important emboli

■ decreased detection of incidentalomas commonly found on CT

• not valid for assessment of PE when patients have consolidation and the test can be limited by

ventilatory problems (e.g COPD), much like CT

• modified V/Q scan (perfusion only, lower dose contrast) may be used for pregnant patients if CXR is

normal or if there are ventilatory problems

Cardiac

Myocardial Perfusion Scanning

• to investigate coronary artery disease (CAD), assess treatment of CAD pre-op risk stratification,

viability testing

• 99mTc-sestamibi, or 99mTc-tetrofosmin are used most commonly, thallium 201 was used previously but

largely discontinued due to high radiation doses to patients and unfavourable imaging characteristics;

today thallium still used for viability studies

• injected at peak exercise (85% max predicted heart rate by the Bruce protocol, chest pain, ECG changes)

or after persantine challenge (vasodilator), or after dobutamine infusion (chronotropic, again to

85% predicted heart rate); can be done as stress only protocol with optional rest or as stress and rest

combined protocol (i.e as 1 day or 2 day protocol)

• patients with left bundle usually given pharmacologic stress because ECG is difficult to interpret for ST

changes and avoids a characteristic artifact

• pharmacologic stress contraindicated if sBP is <90; persantine exacerbates asthma, so patients with

asthma and wheeze who cannot exercise usually get dobutamine infusion; reverse persantine with

aminophylline or caffeine

• persistent defect (at rest and stress) suggests infarction or myocardial scar; reversible defect (only during

stress) suggests ischemia

• used to discriminate between reversible (ischemia) vs irreversible (infarction) changes when other

investigations are equivocal

• Courage trial indicates that patients with >10% ischemic myocardium benefit most from

revascularization

• see Cardiology and Cardiac Surgery, C13

Ventilation Scan Defects Indicate…

ABC TumoUr Airway obstruction Bronchospasm Chronic lung disease Tumour mass obstruction

Perfusion Scan Defects Indicate…

Reduced blood flow due to PE COPD

Asthma Bronchogenic carcinoma Inflammatory lung diseases (pneumonia, sarcoidosis)

Mediastinitis Mucous plug Vasculitis

Nuclear Medicine

Radionuclide Ventriculography

• 99mTc-tagged to red blood cells, tagged albumin is also acceptable

• first pass through RV → pulmonary circulation → LV; provides information about RV function,

presence of shunts

• cardiac MUGA scan sums multiple cardiac cycles, usually at least 200 beats

• evaluation of LV function and regional wall motion, ejection fraction

• images are obtained by gating (synchronizing) the count acquisitions to the ECG signal

• can assess diastolic dysfunction

• provides information on ejection fraction (normal = 50-65%), ventricular volume, and wall motion

• indications: most commonly to monitor potential cardiac toxicity with chemotherapy or herceptin, as a

gold standard of ejection fraction in defibrillator workup

Abdomen and Genitourinary System

HIDA Scan (Cholescintigraphy)

• IV injection of 99mTc-disofenin (DISIDA) or 99mTc-mebrofenin which is bound to protein, taken up, and

excreted by hepatocytes into biliary system

• can be performed in non-fasting state but prefer NPO after midnight

• indicated in workup of cholecystitis when abdominal ultrasound result is equivocal:

■ acute cholecystitis: no visualization of gallbladder at 4 h or 1 h after administration of morphine

■ chronic cholecystitis: no visualization of gallbladder at 1 h but seen at 4 h or after morphine

administration

• gallbladder visualized when cystic duct is patent (rules out acute cholecystitis with >99% certainty),

usually seen by 30 min-1 h

• differential diagnosis of obstructed cystic duct: acute/chronic cholecystitis, decreased hepatobiliary

function (commonly due to alcoholism), bile duct obstruction, parenteral nutrition, fasting less than 4 h

or more than 24 h

• also used to assess bile leaks post-operatively or in trauma

• gallbladder ejection fraction (>38% is normal) can be measured after a fatty meal or CCK to assess for

biliary dyskinesia

RBC Scan

• IV injection of radiotracer with sequential images of the abdomen (99mTc RBCs)

• GI bleed

■ if bleeding acutely at <0.5 mL/min, the focus of activity in the images generally indicates the site

of the acute bleed, look for a change in shape and location on sequential image, requires active

bleeding to localize

■ if bleeding acutely at >0.5 mL/min, use angiography (more specific)

• liver lesion evaluation

■ hemangioma has characteristic appearance: cold early (limited blood flow to lesion), fills n later

(accumulation of tagged cells greater than surrounding liver parenchyma)

Other Important Nuclear Medicine Abdominal Tests

• Meckel’s Scan: uses 99mm pertechnetate; give patient ranitidine premedication; Meckel’s diverticulum

contains gastric mucosa which will light up at the same time as the stomach and get brighter with time

like stomach

• 111In octreoscan: a somatostatin analog used for evaluation and staging of neuroendocrine tumours

including carcinoid; gastrinoma and carcinoid tend to be more octreotide avid than insulinoma

• iodinated MIBG: a norepinephrine analogue, used for pheochromocytoma, neuroblastoma and

medullary thyroid cancer most commonly; limited cardiac applications as above

• solid and liquid gastric emptying: a standardized solid or liquid meal is labelled, usually with 99m Tc

sulfur colloid and gastric emptying studied over time There are normal ranges for solids and liquids

Urea Breath Test

• indication: diagnosis of gastric Helicobacter pylori infection

• patient administered 14C-labelled urea orally, urea metabolized by H pylori to ammonia and 14CO2,

14C-labled CO2 is measured via plastic filament detectors or liquid scintillation

Functional Renal Imaging

• evaluation of renal function and anatomy using 99mTc DTPA or 99m Tc MAG3

• frequently used to provide index of relative function between two kidneys

• frequently used in adults to assess for UPJ obstruction (by assessing the clearance half time with lasix),

and assess renal transplants or as a nuclear GFR study in patients wanting to donate kidneys

• in children, imaging with 99m Tc DMSA is used to assess for pyelonephritis

• in children, the injection of tracer into the bladder via foley catheter is often used to assess for reflux

booksfre

m boo

e om

Interventional Radiology

Bone

Bone Scan

• isotopes, usually 99mTc-diphosphonate

• radioactive tracer binds to hydroxyapatite of bone matrix

increased binding when increased blood supply to bone and/or high bone turnover (active osteoblasts)

• indications: bone pain of unknown origin, staging or restaging of cancer with boney mets (or primary

bone cancer), imaging of arthroplasty complications like loosening or infection, osteomyelitis imaging

• when used to assess for osteomyelitis, usually done in combination with gallium or white blood cell

scan

• differential diagnosis of positive bone scan: bone metastases (breast, prostate, lung, thyroid), primary

bone tumour, arthritis, fracture, infection, anemia, Paget’s disease

• lytic lesions like multiple myeloma, renal cell cancer, eosinophilic granuloma: typically normal or cold

(false negative); need a skeletal survey

• “superscan”: increased bone uptake and poor renal uptake due to diffuse metastases (breast, prostate) or

metabolic causes (e.g renal osteodystrophy)

• catheter can be placed into a large vessel (e.g aorta, vena cava) for a “flush” or selectively placed into a

branch vessel for more detailed examination of smaller vessels and specific organs

• indications: diagnosis of primary occlusive or stenotic vascular disease, aneurysms, coronary,

carotid and cerebral vascular disease, PE, trauma, bleeding (GI, hemoptysis, hematuria), vascular

malformations, as part of endovascular procedures (endovascular aneurysm repair, thrombolysis,

stenting, and angioplasties)

• complications (<5% of patients): puncture site hematoma, infection, pseudoaneurysm, AV fistula,

dissection, thrombosis, embolic occlusion of a distal vessel

• due to improved technology, non-invasive evaluation of vascular structures is being performed more

frequently (colour Doppler U/S, CTA, and MRA)

• see Neuroradiology, MI18

Percutaneous Transluminal Angioplasty and Stents

• introduction and inflation of a balloon into a stenosed or occluded vessel to restore distal blood supply

• common alternative to surgical bypass grafting with 5 yr patency rates similar to surgery, depending on

site

• renal, iliac, femoral, mesenteric, subclavian, coronary, and carotid artery stenoses are amenable to

treatment

• vascular stents may help imp ove long-term results by keeping the vessel wall patent after angioplasty ;

also used for angioplasty failure or complications

• stent grafts (metal mesh covered with durable fabric) may provide an alternative treatment option for

aneurysms and AV fistulas

• complications: similar to angiography, but also includes vessel rupture

Thrombolytic Therapy

• may be systemic (IV) or catheter directed

• infusion of a fibrinolytic agent (urokinase, streptokinase, TNK, tPA – used most commonly) via a

catheter inserted directly into a thrombus

• can restore blood flow in a vessel obstructed with a thrombus or embolus

• indications: treatment of ischemic limb (most common indication), early treatment of MI or stroke to

reduce organ damage, treatment of venous thrombosis (DVT or PE)

• complications: bleeding, stroke, distal embolus, reperfusion injury with myoglobinuria and renal failure

if advanced ischemia present

Embolization

• injection of occluding material into vessels

• permanent agents: amplatzer plugs, coils, glue, and onyx

• temporary: gel foam, autologous blood clots

• indications: management of hemorrhage (epistaxis, trauma, GI bleed, GU bleed), treatment of

arteriovenous malformation, pre-operative treatment of vascular tumours (bone metastases, renal cell

carcinoma), varicocele embolization for infertility, symptomatic uterine fibroids

• complications: post-embolization syndrome (pain, fever, leukocytosis), unintentional embolization of a

non-target organ with resultant ischemia

Thrombolytic Therapy for Pulmonary Embolism

Cochrane Database Syst Rev 2015;(9):CD004437

Purpose: To assess the effects of thrombolytic therapy in

patients with acute pulmonary embolism (PE).

Methods: Systematic review of RCTs evaluating

thrombolytic therapy fo lowed by heparin versus heparin alone, heparin plus placebo or surgical intervention in patients with acute PE Studies comparing two different thrombolytic agents or different doses of the same thrombolytic drug were not considered eligible Main outcomes of interest were death, recurrence of PE, and major and minor hemorrhagic events.

Results: Eighteen trials with2,197 participants were

included Thrombolytics plus heparin were associated with a reduction in odds of death relative to heparin alone

or heparin plus (OR 0.57, 95% CI 0.37 to 0.87, P = 0.02) and recurrence of PE (OR 0.51; 0.29 to 0.89, P = 0.02) Incidence of major and minor hemorrhagic events was statistically significantly higher in the thrombolytics group than the control group (OR 2.90, 95% CI 1.95 to 4.31,

P < 0.001) Length of hospital stay (mean difference (MD) -1.35, -4.27 to 1 58) and qua ity of life were similar between groups Based on one study, stroke occurred more often in the thrombolytics group (OR 12.10, 1.57 to 93.39)

Conclusion: Low-quality evidence suggests thrombolytics

reduce death following acute PE compared with heparin and may be helpful in reducing PE recurrence, but may cause more major and minor hemorrhagic events and stroke events.

Advanced ischemia patients should receive surgery rather than thrombolysis

Chemoembolization delivers chemotherapy directly into the tumour through its feeding blood supply and traps the drug in place by embolization

free

m

Interventional Radiology

Inferior Vena Cava Filter

• insertion of temporary or permanent metallic “umbrellas” to mechanically trap emboli and prevent PE

• inserted via femoral vein, jugular vein, or antecubital vein

• usually placed infrarenally to avoid renal vein thrombosis

• indications: contraindication to anticoagulation, failure of adequate anticoagulation (e.g recurrent PE

despite therapeutic anticoagulant levels), complication of anticoagulation

Central Venous Access

• variety of devices available

• PICC, external tunneled catheter (Hickman or dialysis catheters), subcutaneous port (Portacath®)

• indications: chemotherapy, TPN, long-term antibiotics, administration of fluids and blood products,

• replaces open surgical procedure

• many sites are amenable to biopsy using U/S, fluoroscopy, CT or MR guidance

• complications: false negative (sampling error or tissue necrosis), pneumothorax in 30% of lung biopsies

(chest tube required in ~5%), acute pancreatitis (pancreatic biopsies), bleeding from liver biopsies in

patients with uncorrectable coagulopathies or ascites (can be minimized with transjugular approach)

Abscess Drainage

• placement of a drainage catheter into an infected fluid collection

• administer broad spectrum IV antibiotics prior to procedure

• routes: percutaneous (most common), transgluteal, transvaginal, transrectal

• complications: hemorrhage, injury to intervening structures (e.g bowel), bacteremia, sepsis

Percutaneous Biliary Drainage/Cholecystostomy

• placement of drainage catheter ± metallic stent into obstructed biliary system (PBD) or gallbladder

(cholecystostomy) for relief of jaundice or infection

• percutaneous gallbladder access can be used to crush or remove stones

• indications

■ cholecystostomy: acute cholecystitis

■ PBD biliary obstruction secondary to stone or tumour, cholangitis

• complications

■ acute: sepsis, hemorrhage

■ long-term: tumour ingrowth and stent occlusion

Percutaneous Nephrostomy

• placement of catheter into renal collecting system

• indications: hydronephrosis, pyonephrosis, ureteric injury with or without urinary peritonitis

(traumatic or iatrogenic)

• complications: bacteria and septic shock, hematuria due to pseudoaneurysm or AV fistulas, injury to

adjacent organs

Gastrostomy/Gastrojejunostomy

• percutaneous placement of catheter directly into either stomach (gastrostomy) or through stomach into

small bowel (transgastric jejunostomy)

• indications: inability to eat (most commonly CNS lesion, e.g stroke), esophageal obstruction, or

decompression in gastric outlet obstruction

• complications: gastroesophageal reflux with aspiration peritonitis, hemorrhage, bowel or solid organ

injury

Radiofrequency Ablation

• U/S- or CT-guided probe is inserted into tumour, radiofrequency energy delivered through probe

causes heat deposition and tissue destruction

• indications: hepatic tumours (HCC and metastases), renal tumours

• complications: destruction of neighbouring tissues and structures, bleeding

Indications for Central Venous Access FAT CAB

Fluids Antibiotics TPN Chemotherapy Administration of blood Blood sampling Figure 42 Retrievable IVC filter

Figure 43 Femoral arteriogram: distal occlusion of superficial femoral artery

• x-ray imaging of the breasts for screening in asymptomatic patients, or diagnosis of clinically-detected

or screening-detected abnormalities (see General Surgery, GS56)

• routine evaluation involves two standard views: cranio-caudal and medial-lateral-oblique

Indications

• screening

■ begin screening from age 50 q2-3yr

■ no strong data to support screening >70 yr, but may continue screening if in good general health

■ if <50, screening is only recommended for those with high risk of breast cancer

■ screening detects 2-8 cancers/1,000 women screened

• surveillance

■ follow-up of women with previous breast cancer

• diagnostic: includes mammography with special views and/or ultrasound

■ workup of an abnormality that may be suggestive of breast cancer including a lump or thickening,

localized nodularity, dimpling or contour deformity, a persistent focal area of pain, and spontaneous

serous or sanguinous nipple discharge from a single duct

■ women with abnormal screening mammograms

■ suspected complications of breast implants

Table 20 Breast Imaging Reporting and Data System (BI-RADS ® ) Mammography Categories

Comparison to prior films

Likelihood of malignancy is <2% Unilateral mammogram at 6 mo

Likelihood of malignancy is 95% Biopsy

Breast Ultrasound

Indications

• characterization of palpable abnormalities

■ ultrasound is 1st line <30 yr and in lactating and pregnant women

■ >30 yr need mammogram first

• further characterization of mammographic findings

• guidance for interventional procedures

Breast MRI

Description

• contrast-enhanced MRI of the breasts

• sensitive for detecting invasive breast cancer (95-100%) but specificity variable (37-97%)

• for diagnosis, used only after mammography and U/S investigation

• use as a screening modality is limited to high-risk patients, in conjunction with mammography